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	$185.51	5.839%	$196.3419	$196.34	$196.35	$196.30
Purchase #2	$32.91	11.651%	$36.7443	$36.74	$36.75	$36.70
Purchase #3	$28.34	12.490%	$31.8797	$31.88	$31.90	$31.90
Purchase #4	$110.47	10.451%	$122.0152	$122.02	$122.00	$122.00
Purchase #5	$125.89	13.437%	$142.8058	$142.81	$142.80	$142.80
Purchase #6	$98.30	8.153%	$106.3144	$106.31	$106.30	$106.30
Purchase #7	$84.42	5.229%	$88.8343	$88.83	$88.85	$88.80
7 purchase totals =	$665.84		$724.9356	$724.93	$724.95	$724.80