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	$152.33	12.262%	$171.0087	$171.01	$171.00	$171.00
Purchase #2	$168.81	13.676%	$191.8965	$191.90	$191.90	$191.90
Purchase #3	$141.31	5.246%	$148.7231	$148.72	$148.70	$148.70
Purchase #4	$86.55	8.633%	$94.0219	$94.02	$94.00	$94.00
Purchase #5	$219.38	8.688%	$238.4397	$238.44	$238.45	$238.40
Purchase #6	$165.82	8.867%	$180.5233	$180.52	$180.50	$180.50
Purchase #7	$12.27	11.469%	$13.6772	$13.68	$13.70	$13.70
7 purchase totals =	$946.47		$1,038.2904	$1,038.29	$1,038.25	$1,038.20