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	$105.27	4.231%	$109.724	$109.72	$109.70	$109.70
Purchase #2	$98.59	12.741%	$111.1514	$111.15	$111.15	$111.20
Purchase #3	$187.76	12.842%	$211.8721	$211.87	$211.85	$211.90
Purchase #4	$249.44	4.138%	$259.7618	$259.76	$259.75	$259.80
Purchase #5	$9.62	5.660%	$10.1645	$10.16	$10.15	$10.20
Purchase #6	$193.66	11.769%	$216.4518	$216.45	$216.45	$216.50
Purchase #7	$86.38	13.487%	$98.0301	$98.03	$98.05	$98.00
7 purchase totals =	$930.72		$1,017.1557	$1,017.14	$1,017.10	$1,017.30