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	$62.30	8.540%	$67.6204	$67.62	$67.60	$67.60
Purchase #2	$107.36	11.528%	$119.7365	$119.74	$119.75	$119.70
Purchase #3	$153.71	7.160%	$164.7156	$164.72	$164.70	$164.70
Purchase #4	$177.87	11.256%	$197.891	$197.89	$197.90	$197.90
Purchase #5	$18.76	4.314%	$19.5693	$19.57	$19.55	$19.60
Purchase #6	$132.48	13.315%	$150.1197	$150.12	$150.10	$150.10
Purchase #7	$87.63	3.328%	$90.5463	$90.55	$90.55	$90.50
7 purchase totals =	$740.11		$810.1988	$810.21	$810.15	$810.10