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	$35.76	4.225%	$37.2709	$37.27	$37.25	$37.30
Purchase #2	$40.73	13.584%	$46.2628	$46.26	$46.25	$46.30
Purchase #3	$82.75	4.375%	$86.3703	$86.37	$86.35	$86.40
Purchase #4	$17.38	6.465%	$18.5036	$18.50	$18.50	$18.50
Purchase #5	$17.25	13.195%	$19.5261	$19.53	$19.55	$19.50
Purchase #6	$159.65	9.835%	$175.3516	$175.35	$175.35	$175.40
Purchase #7	$102.46	9.205%	$111.8914	$111.89	$111.90	$111.90
7 purchase totals =	$455.98		$495.1767	$495.17	$495.15	$495.30