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	$84.46	9.111%	$92.1552	$92.16	$92.15	$92.20
Purchase #2	$83.91	7.847%	$90.4944	$90.49	$90.50	$90.50
Purchase #3	$50.97	7.420%	$54.752	$54.75	$54.75	$54.80
Purchase #4	$62.52	11.114%	$69.4685	$69.47	$69.45	$69.50
Purchase #5	$135.33	9.600%	$148.3217	$148.32	$148.30	$148.30
Purchase #6	$147.89	4.358%	$154.335	$154.34	$154.35	$154.30
Purchase #7	$100.99	4.842%	$105.8799	$105.88	$105.90	$105.90
7 purchase totals =	$666.07		$715.4067	$715.41	$715.40	$715.50