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	$127.59	13.328%	$144.5952	$144.60	$144.60	$144.60
Purchase #2	$141.62	4.204%	$147.5737	$147.57	$147.55	$147.60
Purchase #3	$210.32	8.124%	$227.4064	$227.41	$227.40	$227.40
Purchase #4	$190.58	3.396%	$197.0521	$197.05	$197.05	$197.10
Purchase #5	$88.81	11.807%	$99.2958	$99.30	$99.30	$99.30
Purchase #6	$66.85	7.872%	$72.1124	$72.11	$72.10	$72.10
Purchase #7	$162.43	10.402%	$179.326	$179.33	$179.35	$179.30
7 purchase totals =	$988.20		$1,067.3616	$1,067.37	$1,067.35	$1,067.40