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	$43.83	6.209%	$46.5514	$46.55	$46.55	$46.60
Purchase #2	$162.60	7.330%	$174.5186	$174.52	$174.50	$174.50
Purchase #3	$173.74	8.408%	$188.3481	$188.35	$188.35	$188.30
Purchase #4	$110.73	11.773%	$123.7662	$123.77	$123.75	$123.80
Purchase #5	$71.94	3.757%	$74.6428	$74.64	$74.65	$74.60
Purchase #6	$55.94	11.741%	$62.5079	$62.51	$62.50	$62.50
Purchase #7	$54.54	5.740%	$57.6706	$57.67	$57.65	$57.70
7 purchase totals =	$673.32		$728.0056	$728.01	$727.95	$728.00