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	$141.38	7.743%	$152.3271	$152.33	$152.35	$152.30
Purchase #2	$126.73	11.396%	$141.1722	$141.17	$141.15	$141.20
Purchase #3	$42.33	10.217%	$46.6549	$46.65	$46.65	$46.70
Purchase #4	$137.97	7.849%	$148.7993	$148.80	$148.80	$148.80
Purchase #5	$147.48	11.275%	$164.1084	$164.11	$164.10	$164.10
Purchase #6	$215.95	9.647%	$236.7827	$236.78	$236.80	$236.80
Purchase #7	$238.47	4.623%	$249.4945	$249.49	$249.50	$249.50
7 purchase totals =	$1,050.31		$1,139.3391	$1,139.33	$1,139.35	$1,139.40