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	$57.51	13.615%	$65.34	$65.34	$65.35	$65.30
Purchase #2	$84.53	5.680%	$89.3313	$89.33	$89.35	$89.30
Purchase #3	$170.49	12.332%	$191.5148	$191.51	$191.50	$191.50
Purchase #4	$221.59	6.220%	$235.3729	$235.37	$235.35	$235.40
Purchase #5	$152.94	9.870%	$168.0352	$168.04	$168.05	$168.00
Purchase #6	$96.28	8.619%	$104.5784	$104.58	$104.60	$104.60
Purchase #7	$179.37	10.130%	$197.5402	$197.54	$197.55	$197.50
7 purchase totals =	$962.71		$1,051.7128	$1,051.71	$1,051.75	$1,051.60