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	$119.69	6.248%	$127.1682	$127.17	$127.15	$127.20
Purchase #2	$220.69	12.596%	$248.4881	$248.49	$248.50	$248.50
Purchase #3	$86.65	3.459%	$89.6472	$89.65	$89.65	$89.60
Purchase #4	$67.46	5.716%	$71.316	$71.32	$71.30	$71.30
Purchase #5	$106.94	4.490%	$111.7416	$111.74	$111.75	$111.70
Purchase #6	$66.26	9.332%	$72.4434	$72.44	$72.45	$72.40
Purchase #7	$195.73	13.257%	$221.6779	$221.68	$221.70	$221.70
7 purchase totals =	$863.42		$942.4824	$942.49	$942.50	$942.40