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	$103.85	8.539%	$112.7178	$112.72	$112.70	$112.70
Purchase #2	$186.28	5.663%	$196.829	$196.83	$196.85	$196.80
Purchase #3	$18.74	9.526%	$20.5252	$20.53	$20.55	$20.50
Purchase #4	$40.37	8.634%	$43.8555	$43.86	$43.85	$43.90
Purchase #5	$60.81	3.208%	$62.7608	$62.76	$62.75	$62.80
Purchase #6	$247.48	11.237%	$275.2893	$275.29	$275.30	$275.30
Purchase #7	$198.82	11.209%	$221.1057	$221.11	$221.10	$221.10
7 purchase totals =	$856.35		$933.0833	$933.10	$933.10	$933.10