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	$29.50	13.479%	$33.4763	$33.48	$33.50	$33.50
Purchase #2	$189.84	12.376%	$213.3346	$213.33	$213.35	$213.30
Purchase #3	$228.29	10.567%	$252.4134	$252.41	$252.40	$252.40
Purchase #4	$64.93	11.439%	$72.3573	$72.36	$72.35	$72.40
Purchase #5	$210.56	6.113%	$223.4315	$223.43	$223.45	$223.40
Purchase #6	$242.85	6.396%	$258.3827	$258.38	$258.40	$258.40
Purchase #7	$141.47	11.842%	$158.2229	$158.22	$158.20	$158.20
7 purchase totals =	$1,107.44		$1,211.6187	$1,211.61	$1,211.65	$1,211.60