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	$150.40	11.578%	$167.8133	$167.81	$167.80	$167.80
Purchase #2	$208.78	7.796%	$225.0565	$225.06	$225.05	$225.10
Purchase #3	$57.31	4.161%	$59.6947	$59.69	$59.70	$59.70
Purchase #4	$78.42	12.303%	$88.068	$88.07	$88.05	$88.10
Purchase #5	$64.73	6.237%	$68.7672	$68.77	$68.75	$68.80
Purchase #6	$96.41	3.303%	$99.5944	$99.59	$99.60	$99.60
Purchase #7	$179.52	3.286%	$185.419	$185.42	$185.40	$185.40
7 purchase totals =	$835.57		$894.4131	$894.41	$894.35	$894.50