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	$208.60	6.629%	$222.4281	$222.43	$222.45	$222.40
Purchase #2	$189.29	6.610%	$201.8021	$201.80	$201.80	$201.80
Purchase #3	$161.37	6.429%	$171.7445	$171.74	$171.75	$171.70
Purchase #4	$105.59	12.120%	$118.3875	$118.39	$118.40	$118.40
Purchase #5	$220.57	6.213%	$234.274	$234.27	$234.25	$234.30
Purchase #6	$104.87	6.110%	$111.2776	$111.28	$111.30	$111.30
Purchase #7	$86.91	6.320%	$92.4027	$92.40	$92.40	$92.40
7 purchase totals =	$1,077.20		$1,152.3165	$1,152.31	$1,152.35	$1,152.30