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	$123.44	7.138%	$132.2511	$132.25	$132.25	$132.30
Purchase #2	$56.61	10.128%	$62.3435	$62.34	$62.35	$62.30
Purchase #3	$84.61	5.385%	$89.1662	$89.17	$89.15	$89.20
Purchase #4	$189.42	12.143%	$212.4213	$212.42	$212.40	$212.40
Purchase #5	$128.55	13.853%	$146.358	$146.36	$146.35	$146.40
Purchase #6	$136.66	11.636%	$152.5618	$152.56	$152.55	$152.60
Purchase #7	$110.68	6.709%	$118.1055	$118.11	$118.10	$118.10
7 purchase totals =	$829.97		$913.2074	$913.21	$913.15	$913.30