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	$176.50	10.267%	$194.6213	$194.62	$194.60	$194.60
Purchase #2	$79.94	6.631%	$85.2408	$85.24	$85.25	$85.20
Purchase #3	$198.37	11.428%	$221.0397	$221.04	$221.05	$221.00
Purchase #4	$139.49	4.626%	$145.9428	$145.94	$145.95	$145.90
Purchase #5	$136.52	3.816%	$141.7296	$141.73	$141.75	$141.70
Purchase #6	$111.44	12.766%	$125.6664	$125.67	$125.65	$125.70
Purchase #7	$139.62	5.705%	$147.5853	$147.59	$147.60	$147.60
7 purchase totals =	$981.88		$1,061.8259	$1,061.83	$1,061.85	$1,061.70