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	$216.67	10.280%	$238.9437	$238.94	$238.95	$238.90
Purchase #2	$200.91	5.592%	$212.1449	$212.14	$212.15	$212.10
Purchase #3	$42.87	13.211%	$48.5336	$48.53	$48.55	$48.50
Purchase #4	$79.88	11.738%	$89.2563	$89.26	$89.25	$89.30
Purchase #5	$169.40	4.532%	$177.0772	$177.08	$177.10	$177.10
Purchase #6	$72.34	13.580%	$82.1638	$82.16	$82.15	$82.20
Purchase #7	$77.91	13.834%	$88.6881	$88.69	$88.70	$88.70
7 purchase totals =	$859.98		$936.8076	$936.80	$936.85	$936.80