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	$47.77	10.641%	$52.8532	$52.85	$52.85	$52.90
Purchase #2	$102.40	8.624%	$111.231	$111.23	$111.25	$111.20
Purchase #3	$44.70	5.809%	$47.2966	$47.30	$47.30	$47.30
Purchase #4	$193.63	9.760%	$212.5283	$212.53	$212.55	$212.50
Purchase #5	$230.71	10.508%	$254.953	$254.95	$254.95	$255.00
Purchase #6	$232.55	11.682%	$259.7165	$259.72	$259.70	$259.70
Purchase #7	$85.47	6.429%	$90.9649	$90.96	$90.95	$91.00
7 purchase totals =	$937.23		$1,029.5435	$1,029.54	$1,029.55	$1,029.60