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	$95.33	4.706%	$99.8162	$99.82	$99.80	$99.80
Purchase #2	$38.28	4.620%	$40.0485	$40.05	$40.05	$40.00
Purchase #3	$43.71	3.718%	$45.3351	$45.34	$45.35	$45.30
Purchase #4	$247.74	9.424%	$271.087	$271.09	$271.10	$271.10
Purchase #5	$42.54	9.780%	$46.7004	$46.70	$46.70	$46.70
Purchase #6	$167.63	10.401%	$185.0652	$185.07	$185.05	$185.10
Purchase #7	$120.27	9.318%	$131.4768	$131.48	$131.50	$131.50
7 purchase totals =	$755.50		$819.5292	$819.55	$819.55	$819.50