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	$173.95	12.461%	$195.6259	$195.63	$195.65	$195.60
Purchase #2	$115.26	10.142%	$126.9497	$126.95	$126.95	$126.90
Purchase #3	$83.37	8.164%	$90.1763	$90.18	$90.20	$90.20
Purchase #4	$106.33	4.524%	$111.1404	$111.14	$111.15	$111.10
Purchase #5	$123.95	6.396%	$131.8778	$131.88	$131.90	$131.90
Purchase #6	$34.56	12.208%	$38.7791	$38.78	$38.80	$38.80
Purchase #7	$76.77	8.219%	$83.0797	$83.08	$83.10	$83.10
7 purchase totals =	$714.19		$777.6289	$777.64	$777.75	$777.60