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	$132.64	3.799%	$137.679	$137.68	$137.70	$137.70
Purchase #2	$134.77	3.312%	$139.2336	$139.23	$139.25	$139.20
Purchase #3	$55.47	12.438%	$62.3694	$62.37	$62.35	$62.40
Purchase #4	$42.98	13.434%	$48.7539	$48.75	$48.75	$48.80
Purchase #5	$94.71	11.145%	$105.2654	$105.27	$105.25	$105.30
Purchase #6	$106.33	13.391%	$120.5687	$120.57	$120.55	$120.60
Purchase #7	$94.66	6.459%	$100.7741	$100.77	$100.75	$100.80
7 purchase totals =	$661.56		$714.6441	$714.64	$714.60	$714.80