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	$230.45	8.718%	$250.5406	$250.54	$250.55	$250.50
Purchase #2	$68.34	5.145%	$71.8561	$71.86	$71.85	$71.90
Purchase #3	$116.76	6.749%	$124.6401	$124.64	$124.65	$124.60
Purchase #4	$39.59	6.688%	$42.2378	$42.24	$42.25	$42.20
Purchase #5	$71.49	4.834%	$74.9458	$74.95	$74.95	$74.90
Purchase #6	$82.83	4.699%	$86.7222	$86.72	$86.70	$86.70
Purchase #7	$187.83	5.701%	$198.5382	$198.54	$198.55	$198.50
7 purchase totals =	$797.29		$849.4808	$849.49	$849.50	$849.30