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	$147.58	11.791%	$164.9812	$164.98	$165.00	$165.00
Purchase #2	$222.46	13.781%	$253.1172	$253.12	$253.10	$253.10
Purchase #3	$56.67	7.505%	$60.9231	$60.92	$60.90	$60.90
Purchase #4	$209.31	12.468%	$235.4068	$235.41	$235.40	$235.40
Purchase #5	$66.47	8.576%	$72.1705	$72.17	$72.15	$72.20
Purchase #6	$51.71	7.243%	$55.4554	$55.46	$55.45	$55.50
Purchase #7	$79.27	8.461%	$85.977	$85.98	$86.00	$86.00
7 purchase totals =	$833.47		$928.0312	$928.04	$928.00	$928.10