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	$97.37	9.326%	$106.4507	$106.45	$106.45	$106.50
Purchase #2	$163.89	3.207%	$169.146	$169.15	$169.15	$169.10
Purchase #3	$83.32	13.604%	$94.6549	$94.65	$94.65	$94.70
Purchase #4	$35.27	9.132%	$38.4909	$38.49	$38.50	$38.50
Purchase #5	$195.63	11.171%	$217.4838	$217.48	$217.50	$217.50
Purchase #6	$109.79	12.496%	$123.5094	$123.51	$123.50	$123.50
Purchase #7	$191.61	13.871%	$218.1882	$218.19	$218.20	$218.20
7 purchase totals =	$876.88		$967.9239	$967.92	$967.95	$968.00