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	$78.36	9.382%	$85.7117	$85.71	$85.70	$85.70
Purchase #2	$192.47	7.268%	$206.4587	$206.46	$206.45	$206.50
Purchase #3	$99.33	3.511%	$102.8175	$102.82	$102.80	$102.80
Purchase #4	$33.53	5.104%	$35.2414	$35.24	$35.25	$35.20
Purchase #5	$95.30	5.250%	$100.3033	$100.30	$100.30	$100.30
Purchase #6	$92.67	8.461%	$100.5108	$100.51	$100.50	$100.50
Purchase #7	$96.75	7.157%	$103.6744	$103.67	$103.65	$103.70
7 purchase totals =	$688.41		$734.7178	$734.71	$734.65	$734.70