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	$60.41	5.573%	$63.7766	$63.78	$63.80	$63.80
Purchase #2	$108.88	13.810%	$123.9163	$123.92	$123.90	$123.90
Purchase #3	$163.77	10.310%	$180.6547	$180.65	$180.65	$180.70
Purchase #4	$161.38	11.116%	$179.319	$179.32	$179.30	$179.30
Purchase #5	$57.62	11.797%	$64.4174	$64.42	$64.40	$64.40
Purchase #6	$238.45	7.664%	$256.7248	$256.72	$256.70	$256.70
Purchase #7	$211.60	11.111%	$235.1109	$235.11	$235.10	$235.10
7 purchase totals =	$1,002.11		$1,103.9197	$1,103.92	$1,103.85	$1,103.90