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	$230.32	5.363%	$242.6721	$242.67	$242.65	$242.70
Purchase #2	$91.94	8.750%	$99.9848	$99.98	$100.00	$100.00
Purchase #3	$53.62	3.673%	$55.5895	$55.59	$55.60	$55.60
Purchase #4	$44.56	13.216%	$50.449	$50.45	$50.45	$50.40
Purchase #5	$213.39	4.770%	$223.5687	$223.57	$223.55	$223.60
Purchase #6	$105.76	11.874%	$118.3179	$118.32	$118.30	$118.30
Purchase #7	$247.97	9.540%	$271.6263	$271.63	$271.65	$271.60
7 purchase totals =	$987.56		$1,062.2083	$1,062.21	$1,062.20	$1,062.20