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	$228.35	4.628%	$238.918	$238.92	$238.90	$238.90
Purchase #2	$197.69	9.475%	$216.4211	$216.42	$216.40	$216.40
Purchase #3	$48.50	13.220%	$54.9117	$54.91	$54.90	$54.90
Purchase #4	$180.28	6.190%	$191.4393	$191.44	$191.45	$191.40
Purchase #5	$102.62	10.573%	$113.47	$113.47	$113.45	$113.50
Purchase #6	$149.32	11.436%	$166.3962	$166.40	$166.40	$166.40
Purchase #7	$60.93	3.479%	$63.0498	$63.05	$63.05	$63.00
7 purchase totals =	$967.69		$1,044.6061	$1,044.61	$1,044.55	$1,044.50