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	$192.28	4.502%	$200.9364	$200.94	$200.95	$200.90
Purchase #2	$74.46	6.819%	$79.5374	$79.54	$79.55	$79.50
Purchase #3	$55.50	7.746%	$59.799	$59.80	$59.80	$59.80
Purchase #4	$149.99	13.340%	$169.9987	$170.00	$170.00	$170.00
Purchase #5	$100.67	11.825%	$112.5742	$112.57	$112.55	$112.60
Purchase #6	$176.92	11.126%	$196.6041	$196.60	$196.60	$196.60
Purchase #7	$67.83	4.837%	$71.1109	$71.11	$71.10	$71.10
7 purchase totals =	$817.65		$890.5607	$890.56	$890.55	$890.50