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	$194.63	13.825%	$221.5376	$221.54	$221.55	$221.50
Purchase #2	$221.91	5.684%	$234.5234	$234.52	$234.50	$234.50
Purchase #3	$190.34	13.547%	$216.1254	$216.13	$216.15	$216.10
Purchase #4	$114.96	7.278%	$123.3268	$123.33	$123.35	$123.30
Purchase #5	$177.33	10.748%	$196.3894	$196.39	$196.40	$196.40
Purchase #6	$90.69	6.740%	$96.8025	$96.80	$96.80	$96.80
Purchase #7	$218.85	13.183%	$247.701	$247.70	$247.70	$247.70
7 purchase totals =	$1,208.71		$1,336.4061	$1,336.41	$1,336.45	$1,336.30