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	$63.76	12.332%	$71.6229	$71.62	$71.60	$71.60
Purchase #2	$241.65	11.427%	$269.2633	$269.26	$269.25	$269.30
Purchase #3	$196.33	4.478%	$205.1217	$205.12	$205.10	$205.10
Purchase #4	$41.55	13.653%	$47.2228	$47.22	$47.20	$47.20
Purchase #5	$228.71	4.262%	$238.4576	$238.46	$238.45	$238.50
Purchase #6	$148.79	5.369%	$156.7785	$156.78	$156.80	$156.80
Purchase #7	$226.42	5.525%	$238.9297	$238.93	$238.95	$238.90
7 purchase totals =	$1,147.21		$1,227.3965	$1,227.39	$1,227.35	$1,227.40