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	$147.40	5.513%	$155.5262	$155.53	$155.55	$155.50
Purchase #2	$27.33	4.492%	$28.5577	$28.56	$28.55	$28.60
Purchase #3	$246.65	10.210%	$271.833	$271.83	$271.85	$271.80
Purchase #4	$53.28	5.384%	$56.1486	$56.15	$56.15	$56.10
Purchase #5	$59.93	13.165%	$67.8198	$67.82	$67.80	$67.80
Purchase #6	$211.68	3.461%	$219.0062	$219.01	$219.00	$219.00
Purchase #7	$85.56	11.653%	$95.5303	$95.53	$95.55	$95.50
7 purchase totals =	$831.83		$894.4218	$894.43	$894.45	$894.30