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	$107.36	4.317%	$111.9947	$111.99	$112.00	$112.00
Purchase #2	$54.72	11.504%	$61.015	$61.02	$61.00	$61.00
Purchase #3	$31.58	12.869%	$35.644	$35.64	$35.65	$35.60
Purchase #4	$105.66	12.764%	$119.1464	$119.15	$119.15	$119.10
Purchase #5	$63.91	6.231%	$67.8922	$67.89	$67.90	$67.90
Purchase #6	$177.47	4.175%	$184.8794	$184.88	$184.90	$184.90
Purchase #7	$66.77	12.236%	$74.94	$74.94	$74.95	$74.90
7 purchase totals =	$607.47		$655.5117	$655.51	$655.55	$655.40