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	$210.69	12.850%	$237.7637	$237.76	$237.75	$237.80
Purchase #2	$19.70	4.785%	$20.6426	$20.64	$20.65	$20.60
Purchase #3	$42.35	9.863%	$46.527	$46.53	$46.55	$46.50
Purchase #4	$103.89	5.364%	$109.4627	$109.46	$109.45	$109.50
Purchase #5	$165.90	6.585%	$176.8245	$176.82	$176.80	$176.80
Purchase #6	$48.60	3.156%	$50.1338	$50.13	$50.15	$50.10
Purchase #7	$55.33	5.390%	$58.3123	$58.31	$58.30	$58.30
7 purchase totals =	$646.46		$699.6666	$699.65	$699.65	$699.60