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	$182.94	7.571%	$196.7904	$196.79	$196.80	$196.80
Purchase #2	$94.28	5.309%	$99.2853	$99.29	$99.30	$99.30
Purchase #3	$209.71	5.803%	$221.8795	$221.88	$221.90	$221.90
Purchase #4	$121.42	8.336%	$131.5416	$131.54	$131.55	$131.50
Purchase #5	$151.95	11.270%	$169.0748	$169.07	$169.05	$169.10
Purchase #6	$159.57	6.478%	$169.9069	$169.91	$169.90	$169.90
Purchase #7	$217.29	6.683%	$231.8115	$231.81	$231.80	$231.80
7 purchase totals =	$1,137.16		$1,220.2900	$1,220.29	$1,220.30	$1,220.30