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	$114.76	7.210%	$123.0342	$123.03	$123.05	$123.00
Purchase #2	$153.76	5.425%	$162.1015	$162.10	$162.10	$162.10
Purchase #3	$28.89	12.486%	$32.4972	$32.50	$32.50	$32.50
Purchase #4	$107.91	13.299%	$122.261	$122.26	$122.25	$122.30
Purchase #5	$136.67	10.401%	$150.885	$150.89	$150.90	$150.90
Purchase #6	$52.92	11.399%	$58.9524	$58.95	$58.95	$59.00
Purchase #7	$91.84	11.842%	$102.7157	$102.72	$102.70	$102.70
7 purchase totals =	$686.75		$752.4470	$752.45	$752.45	$752.50