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	$141.76	11.234%	$157.6853	$157.69	$157.70	$157.70
Purchase #2	$210.26	10.824%	$233.0185	$233.02	$233.00	$233.00
Purchase #3	$138.63	6.467%	$147.5952	$147.60	$147.60	$147.60
Purchase #4	$125.46	10.700%	$138.8842	$138.88	$138.90	$138.90
Purchase #5	$212.62	6.162%	$225.7216	$225.72	$225.70	$225.70
Purchase #6	$160.48	7.667%	$172.784	$172.78	$172.80	$172.80
Purchase #7	$91.33	13.473%	$103.6349	$103.63	$103.65	$103.60
7 purchase totals =	$1,080.54		$1,179.3237	$1,179.32	$1,179.35	$1,179.30