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	$216.98	12.853%	$244.8684	$244.87	$244.85	$244.90
Purchase #2	$235.94	7.674%	$254.046	$254.05	$254.05	$254.00
Purchase #3	$91.44	9.635%	$100.2502	$100.25	$100.25	$100.30
Purchase #4	$206.98	8.533%	$224.6416	$224.64	$224.65	$224.60
Purchase #5	$115.53	11.342%	$128.6334	$128.63	$128.65	$128.60
Purchase #6	$48.32	9.306%	$52.8167	$52.82	$52.80	$52.80
Purchase #7	$51.41	8.849%	$55.9593	$55.96	$55.95	$56.00
7 purchase totals =	$966.60		$1,061.2156	$1,061.22	$1,061.20	$1,061.20