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	$99.39	4.304%	$103.6677	$103.67	$103.65	$103.70
Purchase #2	$240.30	4.469%	$251.039	$251.04	$251.05	$251.00
Purchase #3	$33.33	11.374%	$37.121	$37.12	$37.10	$37.10
Purchase #4	$208.69	6.792%	$222.8642	$222.86	$222.85	$222.90
Purchase #5	$65.61	11.858%	$73.39	$73.39	$73.40	$73.40
Purchase #6	$139.52	5.717%	$147.4964	$147.50	$147.50	$147.50
Purchase #7	$56.93	13.825%	$64.8006	$64.80	$64.80	$64.80
7 purchase totals =	$843.77		$900.3789	$900.38	$900.35	$900.40