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	$201.47	10.688%	$223.0031	$223.00	$223.00	$223.00
Purchase #2	$125.60	5.799%	$132.8835	$132.88	$132.90	$132.90
Purchase #3	$96.83	11.354%	$107.8241	$107.82	$107.80	$107.80
Purchase #4	$88.42	4.874%	$92.7296	$92.73	$92.75	$92.70
Purchase #5	$151.85	13.681%	$172.6246	$172.62	$172.60	$172.60
Purchase #6	$231.54	7.253%	$248.3336	$248.33	$248.35	$248.30
Purchase #7	$108.93	13.754%	$123.9122	$123.91	$123.90	$123.90
7 purchase totals =	$1,004.64		$1,101.3107	$1,101.29	$1,101.30	$1,101.20