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	$133.44	11.367%	$148.6081	$148.61	$148.60	$148.60
Purchase #2	$77.47	13.501%	$87.9292	$87.93	$87.95	$87.90
Purchase #3	$250.85	13.708%	$285.2365	$285.24	$285.25	$285.20
Purchase #4	$46.49	11.320%	$51.7527	$51.75	$51.75	$51.80
Purchase #5	$37.78	11.112%	$41.9781	$41.98	$42.00	$42.00
Purchase #6	$154.74	7.568%	$166.4507	$166.45	$166.45	$166.50
Purchase #7	$85.41	5.811%	$90.3732	$90.37	$90.35	$90.40
7 purchase totals =	$786.18		$872.3285	$872.33	$872.35	$872.40