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	$166.39	9.729%	$182.5781	$182.58	$182.60	$182.60
Purchase #2	$74.40	9.311%	$81.3274	$81.33	$81.35	$81.30
Purchase #3	$139.77	4.725%	$146.3741	$146.37	$146.35	$146.40
Purchase #4	$123.41	6.428%	$131.3428	$131.34	$131.35	$131.30
Purchase #5	$143.58	4.282%	$149.7281	$149.73	$149.75	$149.70
Purchase #6	$99.53	12.288%	$111.7602	$111.76	$111.75	$111.80
Purchase #7	$84.50	9.175%	$92.2529	$92.25	$92.25	$92.30
7 purchase totals =	$831.58		$895.3636	$895.36	$895.40	$895.40