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	$174.70	8.687%	$189.8762	$189.88	$189.90	$189.90
Purchase #2	$139.89	13.118%	$158.2408	$158.24	$158.25	$158.20
Purchase #3	$130.79	8.270%	$141.6063	$141.61	$141.60	$141.60
Purchase #4	$235.75	9.626%	$258.4433	$258.44	$258.45	$258.40
Purchase #5	$93.87	9.628%	$102.9078	$102.91	$102.90	$102.90
Purchase #6	$80.44	12.842%	$90.7701	$90.77	$90.75	$90.80
Purchase #7	$120.80	7.504%	$129.8648	$129.86	$129.85	$129.90
7 purchase totals =	$976.24		$1,071.7093	$1,071.71	$1,071.70	$1,071.70