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	$35.69	3.220%	$36.8392	$36.84	$36.85	$36.80
Purchase #2	$55.61	7.148%	$59.585	$59.59	$59.60	$59.60
Purchase #3	$93.62	6.590%	$99.7896	$99.79	$99.80	$99.80
Purchase #4	$139.43	12.623%	$157.0302	$157.03	$157.05	$157.00
Purchase #5	$204.68	5.475%	$215.8862	$215.89	$215.90	$215.90
Purchase #6	$12.84	11.242%	$14.2835	$14.28	$14.30	$14.30
Purchase #7	$21.46	4.749%	$22.4791	$22.48	$22.50	$22.50
7 purchase totals =	$563.33		$605.8928	$605.90	$606.00	$605.90