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	$120.89	13.539%	$137.2573	$137.26	$137.25	$137.30
Purchase #2	$30.41	4.359%	$31.7356	$31.74	$31.75	$31.70
Purchase #3	$125.88	5.473%	$132.7694	$132.77	$132.75	$132.80
Purchase #4	$250.51	5.582%	$264.4935	$264.49	$264.50	$264.50
Purchase #5	$33.65	7.457%	$36.1593	$36.16	$36.15	$36.20
Purchase #6	$153.82	10.472%	$169.928	$169.93	$169.95	$169.90
Purchase #7	$128.54	10.865%	$142.5059	$142.51	$142.50	$142.50
7 purchase totals =	$843.70		$914.8490	$914.86	$914.85	$914.90