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	$146.39	4.172%	$152.4974	$152.50	$152.50	$152.50
Purchase #2	$123.28	5.663%	$130.2613	$130.26	$130.25	$130.30
Purchase #3	$217.74	5.619%	$229.9748	$229.97	$229.95	$230.00
Purchase #4	$92.42	8.804%	$100.5567	$100.56	$100.55	$100.60
Purchase #5	$235.87	3.473%	$244.0618	$244.06	$244.05	$244.10
Purchase #6	$74.57	10.410%	$82.3327	$82.33	$82.35	$82.30
Purchase #7	$195.32	12.415%	$219.569	$219.57	$219.55	$219.60
7 purchase totals =	$1,085.59		$1,159.2537	$1,159.25	$1,159.20	$1,159.40