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	$101.85	11.738%	$113.8052	$113.81	$113.80	$113.80
Purchase #2	$55.41	9.731%	$60.8019	$60.80	$60.80	$60.80
Purchase #3	$33.39	5.541%	$35.2401	$35.24	$35.25	$35.20
Purchase #4	$57.25	10.487%	$63.2538	$63.25	$63.25	$63.30
Purchase #5	$188.59	11.196%	$209.7045	$209.70	$209.70	$209.70
Purchase #6	$84.92	5.767%	$89.8173	$89.82	$89.80	$89.80
Purchase #7	$127.91	4.679%	$133.8949	$133.89	$133.90	$133.90
7 purchase totals =	$649.32		$706.5177	$706.51	$706.50	$706.50