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	$48.35	8.868%	$52.6377	$52.64	$52.65	$52.60
Purchase #2	$106.88	3.428%	$110.5438	$110.54	$110.55	$110.50
Purchase #3	$246.66	7.216%	$264.459	$264.46	$264.45	$264.50
Purchase #4	$127.38	11.350%	$141.8376	$141.84	$141.85	$141.80
Purchase #5	$43.52	6.771%	$46.4667	$46.47	$46.45	$46.50
Purchase #6	$50.64	6.469%	$53.9159	$53.92	$53.90	$53.90
Purchase #7	$189.63	4.690%	$198.5236	$198.52	$198.50	$198.50
7 purchase totals =	$813.06		$868.3843	$868.39	$868.35	$868.30