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	$223.29	12.653%	$251.5429	$251.54	$251.55	$251.50
Purchase #2	$18.52	3.386%	$19.1471	$19.15	$19.15	$19.10
Purchase #3	$65.32	9.321%	$71.4085	$71.41	$71.40	$71.40
Purchase #4	$249.32	10.618%	$275.7928	$275.79	$275.80	$275.80
Purchase #5	$39.26	11.833%	$43.9056	$43.91	$43.90	$43.90
Purchase #6	$183.77	3.108%	$189.4816	$189.48	$189.50	$189.50
Purchase #7	$39.37	13.654%	$44.7456	$44.75	$44.75	$44.70
7 purchase totals =	$818.85		$896.0241	$896.03	$896.05	$895.90