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	$221.62	7.668%	$238.6138	$238.61	$238.60	$238.60
Purchase #2	$209.73	11.532%	$233.9161	$233.92	$233.90	$233.90
Purchase #3	$127.62	4.838%	$133.7943	$133.79	$133.80	$133.80
Purchase #4	$55.25	7.428%	$59.354	$59.35	$59.35	$59.40
Purchase #5	$239.80	8.102%	$259.2286	$259.23	$259.25	$259.20
Purchase #6	$72.53	13.107%	$82.0365	$82.04	$82.05	$82.00
Purchase #7	$144.58	3.715%	$149.9511	$149.95	$149.95	$150.00
7 purchase totals =	$1,071.13		$1,156.8944	$1,156.89	$1,156.90	$1,156.90