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	$223.95	9.544%	$245.3238	$245.32	$245.30	$245.30
Purchase #2	$106.88	7.847%	$115.2669	$115.27	$115.25	$115.30
Purchase #3	$184.33	3.405%	$190.6064	$190.61	$190.60	$190.60
Purchase #4	$129.54	10.591%	$143.2596	$143.26	$143.25	$143.30
Purchase #5	$212.83	9.596%	$233.2532	$233.25	$233.25	$233.30
Purchase #6	$126.31	11.479%	$140.8091	$140.81	$140.80	$140.80
Purchase #7	$170.48	11.624%	$190.2966	$190.30	$190.30	$190.30
7 purchase totals =	$1,154.32		$1,258.8156	$1,258.82	$1,258.75	$1,258.90