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	$130.79	11.687%	$146.0754	$146.08	$146.10	$146.10
Purchase #2	$45.62	5.417%	$48.0912	$48.09	$48.10	$48.10
Purchase #3	$55.98	9.265%	$61.1665	$61.17	$61.15	$61.20
Purchase #4	$100.36	11.501%	$111.9024	$111.90	$111.90	$111.90
Purchase #5	$149.93	9.560%	$164.2633	$164.26	$164.25	$164.30
Purchase #6	$81.90	9.648%	$89.8017	$89.80	$89.80	$89.80
Purchase #7	$133.57	4.637%	$139.7636	$139.76	$139.75	$139.80
7 purchase totals =	$698.15		$761.0641	$761.06	$761.05	$761.20