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	$152.59	11.219%	$169.7091	$169.71	$169.70	$169.70
Purchase #2	$110.51	9.243%	$120.7244	$120.72	$120.70	$120.70
Purchase #3	$13.56	9.699%	$14.8752	$14.88	$14.90	$14.90
Purchase #4	$181.62	5.635%	$191.8543	$191.85	$191.85	$191.90
Purchase #5	$245.99	10.836%	$272.6455	$272.65	$272.65	$272.60
Purchase #6	$57.49	3.449%	$59.4728	$59.47	$59.45	$59.50
Purchase #7	$19.48	12.396%	$21.8947	$21.89	$21.90	$21.90
7 purchase totals =	$781.24		$851.1760	$851.17	$851.15	$851.20