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	$157.63	6.624%	$168.0714	$168.07	$168.05	$168.10
Purchase #2	$30.61	13.350%	$34.6964	$34.70	$34.70	$34.70
Purchase #3	$236.58	11.661%	$264.1676	$264.17	$264.15	$264.20
Purchase #4	$159.57	12.685%	$179.8115	$179.81	$179.80	$179.80
Purchase #5	$128.78	11.216%	$143.224	$143.22	$143.20	$143.20
Purchase #6	$191.39	13.142%	$216.5425	$216.54	$216.55	$216.50
Purchase #7	$95.49	3.532%	$98.8627	$98.86	$98.85	$98.90
7 purchase totals =	$1,000.05		$1,105.3761	$1,105.37	$1,105.30	$1,105.40