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	$78.52	7.685%	$84.5543	$84.55	$84.55	$84.60
Purchase #2	$134.61	3.595%	$139.4492	$139.45	$139.45	$139.40
Purchase #3	$49.44	11.814%	$55.2808	$55.28	$55.30	$55.30
Purchase #4	$137.52	9.141%	$150.0907	$150.09	$150.10	$150.10
Purchase #5	$69.39	3.628%	$71.9075	$71.91	$71.90	$71.90
Purchase #6	$192.31	4.224%	$200.4332	$200.43	$200.45	$200.40
Purchase #7	$231.54	7.205%	$248.2225	$248.22	$248.20	$248.20
7 purchase totals =	$893.33		$949.9382	$949.93	$949.95	$949.90