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	$76.31	9.576%	$83.6174	$83.62	$83.60	$83.60
Purchase #2	$100.48	4.768%	$105.2709	$105.27	$105.25	$105.30
Purchase #3	$77.38	11.524%	$86.2973	$86.30	$86.30	$86.30
Purchase #4	$160.51	6.390%	$170.7666	$170.77	$170.75	$170.80
Purchase #5	$221.93	7.796%	$239.2317	$239.23	$239.25	$239.20
Purchase #6	$235.55	5.605%	$248.7526	$248.75	$248.75	$248.80
Purchase #7	$79.73	12.498%	$89.6947	$89.69	$89.70	$89.70
7 purchase totals =	$951.89		$1,023.6312	$1,023.63	$1,023.60	$1,023.70