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	$95.91	3.325%	$99.099	$99.10	$99.10	$99.10
Purchase #2	$8.69	6.796%	$9.2806	$9.28	$9.30	$9.30
Purchase #3	$219.41	13.434%	$248.8855	$248.89	$248.90	$248.90
Purchase #4	$38.71	10.423%	$42.7447	$42.74	$42.75	$42.70
Purchase #5	$198.68	3.220%	$205.0775	$205.08	$205.10	$205.10
Purchase #6	$209.65	9.520%	$229.6087	$229.61	$229.60	$229.60
Purchase #7	$244.78	4.356%	$255.4426	$255.44	$255.45	$255.40
7 purchase totals =	$1,015.83		$1,090.1386	$1,090.14	$1,090.20	$1,090.10