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	$77.51	11.628%	$86.5229	$86.52	$86.50	$86.50
Purchase #2	$217.69	4.566%	$227.6297	$227.63	$227.65	$227.60
Purchase #3	$135.45	6.660%	$144.471	$144.47	$144.45	$144.50
Purchase #4	$46.29	8.344%	$50.1524	$50.15	$50.15	$50.20
Purchase #5	$155.41	12.870%	$175.4113	$175.41	$175.40	$175.40
Purchase #6	$217.38	5.333%	$228.9729	$228.97	$228.95	$229.00
Purchase #7	$62.92	3.873%	$65.3569	$65.36	$65.35	$65.40
7 purchase totals =	$912.65		$978.5171	$978.51	$978.45	$978.60