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	$179.80	5.753%	$190.1439	$190.14	$190.15	$190.10
Purchase #2	$128.65	10.512%	$142.1737	$142.17	$142.15	$142.20
Purchase #3	$127.73	13.597%	$145.0974	$145.10	$145.10	$145.10
Purchase #4	$109.89	13.428%	$124.646	$124.65	$124.65	$124.60
Purchase #5	$75.52	11.188%	$83.9692	$83.97	$83.95	$84.00
Purchase #6	$189.62	13.592%	$215.3932	$215.39	$215.40	$215.40
Purchase #7	$110.76	5.384%	$116.7233	$116.72	$116.70	$116.70
7 purchase totals =	$921.97		$1,018.1467	$1,018.14	$1,018.10	$1,018.10