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	$46.61	11.423%	$51.9343	$51.93	$51.95	$51.90
Purchase #2	$157.83	6.743%	$168.4725	$168.47	$168.45	$168.50
Purchase #3	$190.78	11.574%	$212.8609	$212.86	$212.85	$212.90
Purchase #4	$83.42	9.576%	$91.4083	$91.41	$91.40	$91.40
Purchase #5	$139.71	7.483%	$150.1645	$150.16	$150.15	$150.20
Purchase #6	$138.91	9.173%	$151.6522	$151.65	$151.65	$151.70
Purchase #7	$248.57	9.134%	$271.2744	$271.27	$271.25	$271.30
7 purchase totals =	$1,005.83		$1,097.7671	$1,097.75	$1,097.70	$1,097.90