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	$85.58	13.614%	$97.2309	$97.23	$97.25	$97.20
Purchase #2	$142.31	3.662%	$147.5214	$147.52	$147.50	$147.50
Purchase #3	$46.89	13.522%	$53.2305	$53.23	$53.25	$53.20
Purchase #4	$198.91	12.521%	$223.8155	$223.82	$223.80	$223.80
Purchase #5	$99.76	5.575%	$105.3216	$105.32	$105.30	$105.30
Purchase #6	$6.34	8.575%	$6.8837	$6.88	$6.90	$6.90
Purchase #7	$172.98	4.411%	$180.6101	$180.61	$180.60	$180.60
7 purchase totals =	$752.77		$814.6137	$814.61	$814.60	$814.50