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	$173.47	12.549%	$195.2388	$195.24	$195.25	$195.20
Purchase #2	$188.60	11.785%	$210.8265	$210.83	$210.85	$210.80
Purchase #3	$221.94	13.504%	$251.9108	$251.91	$251.90	$251.90
Purchase #4	$72.41	13.444%	$82.1448	$82.14	$82.15	$82.10
Purchase #5	$77.35	5.651%	$81.721	$81.72	$81.70	$81.70
Purchase #6	$179.57	6.408%	$191.0768	$191.08	$191.10	$191.10
Purchase #7	$93.85	10.648%	$103.8431	$103.84	$103.85	$103.80
7 purchase totals =	$1,007.19		$1,116.7618	$1,116.76	$1,116.80	$1,116.60