Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$108.96	7.321%	$116.937	$116.94	$116.95	$116.90
Purchase #2	$220.28	3.171%	$227.2651	$227.27	$227.25	$227.30
Purchase #3	$113.63	4.376%	$118.6024	$118.60	$118.60	$118.60
Purchase #4	$152.53	12.479%	$171.5642	$171.56	$171.55	$171.60
Purchase #5	$171.65	13.680%	$195.1317	$195.13	$195.15	$195.10
Purchase #6	$145.91	4.209%	$152.0514	$152.05	$152.05	$152.10
Purchase #7	$103.55	4.797%	$108.5173	$108.52	$108.50	$108.50
7 purchase totals =	$1,016.51		$1,090.0691	$1,090.07	$1,090.05	$1,090.10