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	$223.67	10.610%	$247.4014	$247.40	$247.40	$247.40
Purchase #2	$132.60	10.441%	$146.4448	$146.44	$146.45	$146.40
Purchase #3	$60.98	6.475%	$64.9285	$64.93	$64.95	$64.90
Purchase #4	$92.63	11.478%	$103.2621	$103.26	$103.25	$103.30
Purchase #5	$115.48	11.261%	$128.4842	$128.48	$128.50	$128.50
Purchase #6	$233.28	4.333%	$243.388	$243.39	$243.40	$243.40
Purchase #7	$226.69	10.706%	$250.9594	$250.96	$250.95	$251.00
7 purchase totals =	$1,085.33		$1,184.8684	$1,184.86	$1,184.90	$1,184.90