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	$142.32	13.242%	$161.166	$161.17	$161.15	$161.20
Purchase #2	$64.74	11.584%	$72.2395	$72.24	$72.25	$72.20
Purchase #3	$103.67	6.618%	$110.5309	$110.53	$110.55	$110.50
Purchase #4	$196.68	10.378%	$217.0915	$217.09	$217.10	$217.10
Purchase #5	$247.81	9.305%	$270.8687	$270.87	$270.85	$270.90
Purchase #6	$148.86	13.190%	$168.4946	$168.49	$168.50	$168.50
Purchase #7	$126.30	12.846%	$142.5245	$142.52	$142.50	$142.50
7 purchase totals =	$1,030.38		$1,142.9157	$1,142.91	$1,142.90	$1,142.90