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	$218.44	3.368%	$225.7971	$225.80	$225.80	$225.80
Purchase #2	$193.87	11.164%	$215.5136	$215.51	$215.50	$215.50
Purchase #3	$72.27	11.401%	$80.5095	$80.51	$80.50	$80.50
Purchase #4	$92.57	4.609%	$96.8366	$96.84	$96.85	$96.80
Purchase #5	$195.58	10.638%	$216.3858	$216.39	$216.40	$216.40
Purchase #6	$223.47	3.567%	$231.4412	$231.44	$231.45	$231.40
Purchase #7	$71.66	12.231%	$80.4247	$80.42	$80.40	$80.40
7 purchase totals =	$1,067.86		$1,146.9085	$1,146.91	$1,146.90	$1,146.80