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	$203.65	3.149%	$210.0629	$210.06	$210.05	$210.10
Purchase #2	$16.74	9.815%	$18.383	$18.38	$18.40	$18.40
Purchase #3	$26.52	3.612%	$27.4779	$27.48	$27.50	$27.50
Purchase #4	$42.83	6.298%	$45.5274	$45.53	$45.55	$45.50
Purchase #5	$39.83	10.146%	$43.8712	$43.87	$43.85	$43.90
Purchase #6	$204.68	8.660%	$222.4053	$222.41	$222.40	$222.40
Purchase #7	$223.40	9.690%	$245.0475	$245.05	$245.05	$245.00
7 purchase totals =	$757.65		$812.7752	$812.78	$812.80	$812.80