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	$175.59	8.716%	$190.8944	$190.89	$190.90	$190.90
Purchase #2	$93.48	3.224%	$96.4938	$96.49	$96.50	$96.50
Purchase #3	$82.61	10.529%	$91.308	$91.31	$91.30	$91.30
Purchase #4	$33.93	4.569%	$35.4803	$35.48	$35.50	$35.50
Purchase #5	$213.96	7.435%	$229.8679	$229.87	$229.85	$229.90
Purchase #6	$108.98	5.261%	$114.7134	$114.71	$114.70	$114.70
Purchase #7	$245.74	13.596%	$279.1508	$279.15	$279.15	$279.20
7 purchase totals =	$954.29		$1,037.9086	$1,037.90	$1,037.90	$1,038.00