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	$211.53	8.125%	$228.7168	$228.72	$228.70	$228.70
Purchase #2	$155.60	12.513%	$175.0702	$175.07	$175.05	$175.10
Purchase #3	$171.74	11.397%	$191.3132	$191.31	$191.30	$191.30
Purchase #4	$24.49	11.821%	$27.385	$27.39	$27.40	$27.40
Purchase #5	$37.51	10.213%	$41.3409	$41.34	$41.35	$41.30
Purchase #6	$215.98	11.498%	$240.8134	$240.81	$240.80	$240.80
Purchase #7	$106.45	4.404%	$111.1381	$111.14	$111.15	$111.10
7 purchase totals =	$923.30		$1,015.7776	$1,015.78	$1,015.75	$1,015.70