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	$140.90	10.545%	$155.7579	$155.76	$155.75	$155.80
Purchase #2	$28.96	11.198%	$32.2029	$32.20	$32.20	$32.20
Purchase #3	$144.30	6.395%	$153.528	$153.53	$153.55	$153.50
Purchase #4	$95.90	4.405%	$100.1244	$100.12	$100.10	$100.10
Purchase #5	$182.50	6.448%	$194.2676	$194.27	$194.25	$194.30
Purchase #6	$126.95	3.790%	$131.7614	$131.76	$131.75	$131.80
Purchase #7	$74.38	9.353%	$81.3368	$81.34	$81.35	$81.30
7 purchase totals =	$793.89		$848.9790	$848.98	$848.95	$849.00