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	$52.66	12.865%	$59.4347	$59.43	$59.45	$59.40
Purchase #2	$239.29	3.262%	$247.0956	$247.10	$247.10	$247.10
Purchase #3	$51.70	3.525%	$53.5224	$53.52	$53.50	$53.50
Purchase #4	$246.27	7.249%	$264.1221	$264.12	$264.10	$264.10
Purchase #5	$13.46	11.305%	$14.9817	$14.98	$15.00	$15.00
Purchase #6	$35.82	11.198%	$39.8311	$39.83	$39.85	$39.80
Purchase #7	$248.94	9.824%	$273.3959	$273.40	$273.40	$273.40
7 purchase totals =	$888.14		$952.3835	$952.38	$952.40	$952.30