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	$208.56	5.506%	$220.0433	$220.04	$220.05	$220.00
Purchase #2	$18.34	12.308%	$20.5973	$20.60	$20.60	$20.60
Purchase #3	$57.41	3.413%	$59.3694	$59.37	$59.35	$59.40
Purchase #4	$194.48	10.698%	$215.2855	$215.29	$215.30	$215.30
Purchase #5	$197.76	12.194%	$221.8749	$221.87	$221.85	$221.90
Purchase #6	$154.61	11.841%	$172.9174	$172.92	$172.90	$172.90
Purchase #7	$44.81	12.413%	$50.3723	$50.37	$50.35	$50.40
7 purchase totals =	$875.97		$960.4601	$960.46	$960.40	$960.50