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	$145.86	11.259%	$162.2824	$162.28	$162.30	$162.30
Purchase #2	$92.70	13.801%	$105.4935	$105.49	$105.50	$105.50
Purchase #3	$42.54	8.238%	$46.0444	$46.04	$46.05	$46.00
Purchase #4	$65.95	9.340%	$72.1097	$72.11	$72.10	$72.10
Purchase #5	$193.91	4.179%	$202.0135	$202.01	$202.00	$202.00
Purchase #6	$233.89	9.846%	$256.9188	$256.92	$256.90	$256.90
Purchase #7	$89.46	8.555%	$97.1133	$97.11	$97.10	$97.10
7 purchase totals =	$864.31		$941.9756	$941.96	$941.95	$941.90