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	$151.26	11.233%	$168.251	$168.25	$168.25	$168.30
Purchase #2	$115.30	3.604%	$119.4554	$119.46	$119.45	$119.50
Purchase #3	$145.96	6.178%	$154.9774	$154.98	$155.00	$155.00
Purchase #4	$116.59	11.772%	$130.315	$130.32	$130.30	$130.30
Purchase #5	$221.25	11.837%	$247.4394	$247.44	$247.45	$247.40
Purchase #6	$58.71	4.442%	$61.3179	$61.32	$61.30	$61.30
Purchase #7	$89.45	4.609%	$93.5728	$93.57	$93.55	$93.60
7 purchase totals =	$898.52		$975.3289	$975.34	$975.30	$975.40