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	$133.89	13.808%	$152.3775	$152.38	$152.40	$152.40
Purchase #2	$79.47	3.815%	$82.5018	$82.50	$82.50	$82.50
Purchase #3	$173.39	9.784%	$190.3545	$190.35	$190.35	$190.40
Purchase #4	$221.74	12.733%	$249.9742	$249.97	$249.95	$250.00
Purchase #5	$42.63	7.607%	$45.8729	$45.87	$45.85	$45.90
Purchase #6	$106.42	13.527%	$120.8154	$120.82	$120.80	$120.80
Purchase #7	$32.67	8.415%	$35.4192	$35.42	$35.40	$35.40
7 purchase totals =	$790.21		$877.3155	$877.31	$877.25	$877.40