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	$181.78	13.220%	$205.8113	$205.81	$205.80	$205.80
Purchase #2	$37.96	7.308%	$40.7341	$40.73	$40.75	$40.70
Purchase #3	$121.76	6.860%	$130.1127	$130.11	$130.10	$130.10
Purchase #4	$224.33	13.683%	$255.0251	$255.03	$255.05	$255.00
Purchase #5	$57.29	4.444%	$59.836	$59.84	$59.85	$59.80
Purchase #6	$124.39	8.751%	$135.2754	$135.28	$135.30	$135.30
Purchase #7	$195.40	13.783%	$222.332	$222.33	$222.35	$222.30
7 purchase totals =	$942.91		$1,049.1266	$1,049.13	$1,049.20	$1,049.00