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	$60.57	10.220%	$66.7603	$66.76	$66.75	$66.80
Purchase #2	$134.93	11.217%	$150.0651	$150.07	$150.05	$150.10
Purchase #3	$159.34	9.299%	$174.157	$174.16	$174.15	$174.20
Purchase #4	$96.32	4.741%	$100.8865	$100.89	$100.90	$100.90
Purchase #5	$75.69	13.707%	$86.0648	$86.06	$86.05	$86.10
Purchase #6	$7.25	13.723%	$8.2449	$8.24	$8.25	$8.20
Purchase #7	$171.35	13.548%	$194.5645	$194.56	$194.55	$194.60
7 purchase totals =	$705.45		$780.7431	$780.74	$780.70	$780.90