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	$125.47	4.538%	$131.1638	$131.16	$131.15	$131.20
Purchase #2	$119.30	3.693%	$123.7057	$123.71	$123.70	$123.70
Purchase #3	$45.97	13.214%	$52.0445	$52.04	$52.05	$52.00
Purchase #4	$144.44	12.621%	$162.6698	$162.67	$162.65	$162.70
Purchase #5	$68.86	3.568%	$71.3169	$71.32	$71.30	$71.30
Purchase #6	$176.48	4.111%	$183.7351	$183.74	$183.75	$183.70
Purchase #7	$18.26	12.816%	$20.6002	$20.60	$20.60	$20.60
7 purchase totals =	$698.78		$745.2360	$745.24	$745.20	$745.20