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	$115.51	6.802%	$123.367	$123.37	$123.35	$123.40
Purchase #2	$208.40	6.872%	$222.7212	$222.72	$222.70	$222.70
Purchase #3	$66.69	4.359%	$69.597	$69.60	$69.60	$69.60
Purchase #4	$65.31	7.530%	$70.2278	$70.23	$70.25	$70.20
Purchase #5	$196.65	4.531%	$205.5602	$205.56	$205.55	$205.60
Purchase #6	$102.92	11.347%	$114.5983	$114.60	$114.60	$114.60
Purchase #7	$87.43	4.788%	$91.6161	$91.62	$91.60	$91.60
7 purchase totals =	$842.91		$897.6876	$897.70	$897.65	$897.70