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	$49.74	7.419%	$53.4302	$53.43	$53.45	$53.40
Purchase #2	$138.92	4.837%	$145.6396	$145.64	$145.65	$145.60
Purchase #3	$234.66	12.730%	$264.5322	$264.53	$264.55	$264.50
Purchase #4	$71.90	7.497%	$77.2903	$77.29	$77.30	$77.30
Purchase #5	$123.88	5.348%	$130.5051	$130.51	$130.50	$130.50
Purchase #6	$84.86	6.438%	$90.3233	$90.32	$90.30	$90.30
Purchase #7	$170.86	12.786%	$192.7062	$192.71	$192.70	$192.70
7 purchase totals =	$874.82		$954.4269	$954.43	$954.45	$954.30