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	$72.27	8.538%	$78.4404	$78.44	$78.45	$78.40
Purchase #2	$25.81	9.742%	$28.3244	$28.32	$28.30	$28.30
Purchase #3	$207.70	8.350%	$225.043	$225.04	$225.05	$225.00
Purchase #4	$212.59	4.297%	$221.725	$221.73	$221.75	$221.70
Purchase #5	$69.25	3.831%	$71.903	$71.90	$71.90	$71.90
Purchase #6	$23.89	4.709%	$25.015	$25.02	$25.00	$25.00
Purchase #7	$99.45	6.309%	$105.7243	$105.72	$105.70	$105.70
7 purchase totals =	$710.96		$756.1751	$756.17	$756.15	$756.00