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	$160.56	9.332%	$175.5435	$175.54	$175.55	$175.50
Purchase #2	$112.41	3.757%	$116.6332	$116.63	$116.65	$116.60
Purchase #3	$142.55	7.847%	$153.7359	$153.74	$153.75	$153.70
Purchase #4	$225.27	8.120%	$243.5619	$243.56	$243.55	$243.60
Purchase #5	$237.54	7.492%	$255.3365	$255.34	$255.35	$255.30
Purchase #6	$33.99	3.815%	$35.2867	$35.29	$35.30	$35.30
Purchase #7	$35.97	4.113%	$37.4494	$37.45	$37.45	$37.40
7 purchase totals =	$948.29		$1,017.5471	$1,017.55	$1,017.60	$1,017.40