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	$101.63	7.177%	$108.924	$108.92	$108.90	$108.90
Purchase #2	$32.57	8.208%	$35.2433	$35.24	$35.25	$35.20
Purchase #3	$85.93	10.647%	$95.079	$95.08	$95.10	$95.10
Purchase #4	$212.92	9.701%	$233.5754	$233.58	$233.60	$233.60
Purchase #5	$174.90	12.220%	$196.2728	$196.27	$196.25	$196.30
Purchase #6	$158.92	7.428%	$170.7246	$170.72	$170.70	$170.70
Purchase #7	$75.72	6.330%	$80.5131	$80.51	$80.50	$80.50
7 purchase totals =	$842.59		$920.3322	$920.32	$920.30	$920.30