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	$158.47	5.659%	$167.4378	$167.44	$167.45	$167.40
Purchase #2	$160.67	4.851%	$168.4641	$168.46	$168.45	$168.50
Purchase #3	$110.38	5.354%	$116.2897	$116.29	$116.30	$116.30
Purchase #4	$113.84	11.303%	$126.7073	$126.71	$126.70	$126.70
Purchase #5	$106.50	9.210%	$116.3087	$116.31	$116.30	$116.30
Purchase #6	$158.39	6.465%	$168.6299	$168.63	$168.65	$168.60
Purchase #7	$57.65	12.196%	$64.681	$64.68	$64.70	$64.70
7 purchase totals =	$865.90		$928.5185	$928.52	$928.55	$928.50