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	$41.58	11.870%	$46.5155	$46.52	$46.50	$46.50
Purchase #2	$119.89	7.511%	$128.8949	$128.89	$128.90	$128.90
Purchase #3	$37.38	9.846%	$41.0604	$41.06	$41.05	$41.10
Purchase #4	$191.71	10.614%	$212.0581	$212.06	$212.05	$212.10
Purchase #5	$43.64	3.829%	$45.311	$45.31	$45.30	$45.30
Purchase #6	$112.36	9.610%	$123.1578	$123.16	$123.15	$123.20
Purchase #7	$132.59	12.752%	$149.4979	$149.50	$149.50	$149.50
7 purchase totals =	$679.15		$746.4956	$746.50	$746.45	$746.60