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	$67.76	4.497%	$70.8072	$70.81	$70.80	$70.80
Purchase #2	$63.31	11.322%	$70.478	$70.48	$70.50	$70.50
Purchase #3	$126.68	3.713%	$131.3836	$131.38	$131.40	$131.40
Purchase #4	$191.55	4.439%	$200.0529	$200.05	$200.05	$200.10
Purchase #5	$240.95	8.831%	$262.2283	$262.23	$262.25	$262.20
Purchase #6	$70.65	3.200%	$72.9108	$72.91	$72.90	$72.90
Purchase #7	$85.68	3.152%	$88.3806	$88.38	$88.40	$88.40
7 purchase totals =	$846.58		$896.2414	$896.24	$896.30	$896.30