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	$180.94	5.446%	$190.794	$190.79	$190.80	$190.80
Purchase #2	$47.54	4.814%	$49.8286	$49.83	$49.85	$49.80
Purchase #3	$64.72	9.520%	$70.8813	$70.88	$70.90	$70.90
Purchase #4	$164.73	4.243%	$171.7195	$171.72	$171.70	$171.70
Purchase #5	$171.54	11.408%	$191.1093	$191.11	$191.10	$191.10
Purchase #6	$125.25	6.115%	$132.909	$132.91	$132.90	$132.90
Purchase #7	$43.83	3.590%	$45.4035	$45.40	$45.40	$45.40
7 purchase totals =	$798.55		$852.6452	$852.64	$852.65	$852.60