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	$188.83	6.302%	$200.7301	$200.73	$200.75	$200.70
Purchase #2	$11.85	3.803%	$12.3007	$12.30	$12.30	$12.30
Purchase #3	$193.33	9.369%	$211.4431	$211.44	$211.45	$211.40
Purchase #4	$13.33	4.105%	$13.8772	$13.88	$13.90	$13.90
Purchase #5	$73.51	6.786%	$78.4984	$78.50	$78.50	$78.50
Purchase #6	$61.77	8.360%	$66.934	$66.93	$66.95	$66.90
Purchase #7	$208.82	11.362%	$232.5461	$232.55	$232.55	$232.50
7 purchase totals =	$751.44		$816.3296	$816.33	$816.40	$816.20