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	7.406%	$83.2504	$83.25	$83.25	$83.30
Purchase #2	$17.87	4.212%	$18.6227	$18.62	$18.60	$18.60
Purchase #3	$138.80	11.539%	$154.8161	$154.82	$154.80	$154.80
Purchase #4	$173.84	12.870%	$196.2132	$196.21	$196.20	$196.20
Purchase #5	$245.71	7.585%	$264.3471	$264.35	$264.35	$264.30
Purchase #6	$237.93	7.772%	$256.4219	$256.42	$256.40	$256.40
Purchase #7	$215.40	12.395%	$242.0988	$242.10	$242.10	$242.10
7 purchase totals =	$1,107.06		$1,215.7702	$1,215.77	$1,215.70	$1,215.70