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	$143.77	11.523%	$160.3366	$160.34	$160.35	$160.30
Purchase #2	$241.74	5.565%	$255.1928	$255.19	$255.20	$255.20
Purchase #3	$200.73	13.786%	$228.4026	$228.40	$228.40	$228.40
Purchase #4	$90.42	6.503%	$96.3	$96.30	$96.30	$96.30
Purchase #5	$55.89	6.711%	$59.6408	$59.64	$59.65	$59.60
Purchase #6	$204.29	13.199%	$231.2542	$231.25	$231.25	$231.30
Purchase #7	$82.44	12.261%	$92.548	$92.55	$92.55	$92.50
7 purchase totals =	$1,019.28		$1,123.6750	$1,123.67	$1,123.70	$1,123.60