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	$93.63	13.108%	$105.903	$105.90	$105.90	$105.90
Purchase #2	$118.69	6.391%	$126.2755	$126.28	$126.30	$126.30
Purchase #3	$230.51	13.282%	$261.1263	$261.13	$261.15	$261.10
Purchase #4	$54.54	13.121%	$61.6962	$61.70	$61.70	$61.70
Purchase #5	$70.76	13.446%	$80.2744	$80.27	$80.25	$80.30
Purchase #6	$146.74	10.430%	$162.045	$162.05	$162.05	$162.00
Purchase #7	$226.96	6.674%	$242.1073	$242.11	$242.10	$242.10
7 purchase totals =	$941.83		$1,039.4277	$1,039.44	$1,039.45	$1,039.40