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	$134.27	12.835%	$151.5036	$151.50	$151.50	$151.50
Purchase #2	$129.46	12.525%	$145.6749	$145.67	$145.65	$145.70
Purchase #3	$159.48	13.611%	$181.1868	$181.19	$181.20	$181.20
Purchase #4	$209.44	4.822%	$219.5392	$219.54	$219.55	$219.50
Purchase #5	$53.55	11.858%	$59.9	$59.90	$59.90	$59.90
Purchase #6	$233.48	4.570%	$244.15	$244.15	$244.15	$244.20
Purchase #7	$219.99	10.753%	$243.6455	$243.65	$243.65	$243.60
7 purchase totals =	$1,139.67		$1,245.6000	$1,245.60	$1,245.60	$1,245.60