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	$196.67	13.287%	$222.8015	$222.80	$222.80	$222.80
Purchase #2	$150.74	10.637%	$166.7742	$166.77	$166.75	$166.80
Purchase #3	$174.98	8.158%	$189.2549	$189.25	$189.25	$189.30
Purchase #4	$222.73	4.404%	$232.539	$232.54	$232.55	$232.50
Purchase #5	$248.78	5.447%	$262.331	$262.33	$262.35	$262.30
Purchase #6	$242.72	3.107%	$250.2613	$250.26	$250.25	$250.30
Purchase #7	$90.78	4.184%	$94.5782	$94.58	$94.60	$94.60
7 purchase totals =	$1,327.40		$1,418.5401	$1,418.53	$1,418.55	$1,418.60