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	$174.87	4.418%	$182.5958	$182.60	$182.60	$182.60
Purchase #2	$89.40	5.507%	$94.3233	$94.32	$94.30	$94.30
Purchase #3	$37.83	7.363%	$40.6154	$40.62	$40.60	$40.60
Purchase #4	$86.66	10.671%	$95.9075	$95.91	$95.90	$95.90
Purchase #5	$152.98	8.738%	$166.3474	$166.35	$166.35	$166.30
Purchase #6	$208.79	7.279%	$223.9878	$223.99	$224.00	$224.00
Purchase #7	$94.92	4.631%	$99.3157	$99.32	$99.30	$99.30
7 purchase totals =	$845.45		$903.0929	$903.11	$903.05	$903.00