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	$227.25	4.837%	$238.2421	$238.24	$238.25	$238.20
Purchase #2	$213.96	7.306%	$229.5919	$229.59	$229.60	$229.60
Purchase #3	$175.95	9.157%	$192.0617	$192.06	$192.05	$192.10
Purchase #4	$12.27	13.341%	$13.9069	$13.91	$13.90	$13.90
Purchase #5	$59.77	10.226%	$65.8821	$65.88	$65.90	$65.90
Purchase #6	$78.83	13.453%	$89.435	$89.44	$89.45	$89.40
Purchase #7	$209.72	3.502%	$217.0644	$217.06	$217.05	$217.10
7 purchase totals =	$977.75		$1,046.1841	$1,046.18	$1,046.20	$1,046.20