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	$65.25	3.151%	$67.306	$67.31	$67.30	$67.30
Purchase #2	$75.72	12.120%	$84.8973	$84.90	$84.90	$84.90
Purchase #3	$100.52	11.744%	$112.3251	$112.33	$112.35	$112.30
Purchase #4	$82.91	8.614%	$90.0519	$90.05	$90.05	$90.10
Purchase #5	$160.49	10.711%	$177.6801	$177.68	$177.70	$177.70
Purchase #6	$51.97	5.607%	$54.884	$54.88	$54.90	$54.90
Purchase #7	$137.46	10.102%	$151.3462	$151.35	$151.35	$151.30
7 purchase totals =	$674.32		$738.4906	$738.50	$738.55	$738.50