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	$31.53	11.820%	$35.2568	$35.26	$35.25	$35.30
Purchase #2	$228.82	13.213%	$259.054	$259.05	$259.05	$259.10
Purchase #3	$104.61	4.731%	$109.5591	$109.56	$109.55	$109.60
Purchase #4	$130.29	13.304%	$147.6238	$147.62	$147.60	$147.60
Purchase #5	$163.78	5.492%	$172.7748	$172.77	$172.75	$172.80
Purchase #6	$204.28	12.367%	$229.5433	$229.54	$229.55	$229.50
Purchase #7	$66.36	3.800%	$68.8817	$68.88	$68.90	$68.90
7 purchase totals =	$929.67		$1,022.6935	$1,022.68	$1,022.65	$1,022.80