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	$169.45	5.594%	$178.929	$178.93	$178.95	$178.90
Purchase #2	$72.34	8.807%	$78.711	$78.71	$78.70	$78.70
Purchase #3	$132.85	13.869%	$151.275	$151.28	$151.30	$151.30
Purchase #4	$183.29	9.453%	$200.6164	$200.62	$200.60	$200.60
Purchase #5	$152.91	11.831%	$171.0008	$171.00	$171.00	$171.00
Purchase #6	$181.85	12.570%	$204.7085	$204.71	$204.70	$204.70
Purchase #7	$97.37	9.341%	$106.4653	$106.47	$106.45	$106.50
7 purchase totals =	$990.06		$1,091.7060	$1,091.72	$1,091.70	$1,091.70