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	$50.89	3.210%	$52.5236	$52.52	$52.50	$52.50
Purchase #2	$150.94	3.459%	$156.161	$156.16	$156.15	$156.20
Purchase #3	$206.98	9.378%	$226.3906	$226.39	$226.40	$226.40
Purchase #4	$93.78	4.223%	$97.7403	$97.74	$97.75	$97.70
Purchase #5	$204.78	3.705%	$212.3671	$212.37	$212.35	$212.40
Purchase #6	$127.49	8.167%	$137.9021	$137.90	$137.90	$137.90
Purchase #7	$134.54	3.598%	$139.3807	$139.38	$139.40	$139.40
7 purchase totals =	$969.40		$1,022.4654	$1,022.46	$1,022.45	$1,022.50