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	$244.29	7.407%	$262.3846	$262.38	$262.40	$262.40
Purchase #2	$199.57	11.436%	$222.3928	$222.39	$222.40	$222.40
Purchase #3	$57.82	10.281%	$63.7645	$63.76	$63.75	$63.80
Purchase #4	$41.29	9.346%	$45.149	$45.15	$45.15	$45.10
Purchase #5	$248.82	13.521%	$282.463	$282.46	$282.45	$282.50
Purchase #6	$17.33	7.839%	$18.6885	$18.69	$18.70	$18.70
Purchase #7	$185.69	13.114%	$210.0414	$210.04	$210.05	$210.00
7 purchase totals =	$994.81		$1,104.8838	$1,104.87	$1,104.90	$1,104.90