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	$196.76	3.559%	$203.7627	$203.76	$203.75	$203.80
Purchase #2	$18.60	11.860%	$20.806	$20.81	$20.80	$20.80
Purchase #3	$136.29	11.152%	$151.4891	$151.49	$151.50	$151.50
Purchase #4	$185.43	11.815%	$207.3386	$207.34	$207.35	$207.30
Purchase #5	$227.56	7.302%	$244.1764	$244.18	$244.20	$244.20
Purchase #6	$123.78	12.654%	$139.4431	$139.44	$139.45	$139.40
Purchase #7	$168.87	9.842%	$185.4902	$185.49	$185.50	$185.50
7 purchase totals =	$1,057.29		$1,152.5061	$1,152.51	$1,152.55	$1,152.50