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	$127.86	3.642%	$132.5167	$132.52	$132.50	$132.50
Purchase #2	$130.89	13.818%	$148.9764	$148.98	$149.00	$149.00
Purchase #3	$82.89	11.674%	$92.5666	$92.57	$92.55	$92.60
Purchase #4	$129.90	11.532%	$144.8801	$144.88	$144.90	$144.90
Purchase #5	$174.72	8.370%	$189.3441	$189.34	$189.35	$189.30
Purchase #6	$66.52	10.771%	$73.6849	$73.68	$73.70	$73.70
Purchase #7	$83.39	13.280%	$94.4642	$94.46	$94.45	$94.50
7 purchase totals =	$796.17		$876.4330	$876.43	$876.45	$876.50