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	$78.69	3.839%	$81.7109	$81.71	$81.70	$81.70
Purchase #2	$245.64	4.415%	$256.485	$256.49	$256.50	$256.50
Purchase #3	$67.34	6.764%	$71.8949	$71.89	$71.90	$71.90
Purchase #4	$135.33	4.714%	$141.7095	$141.71	$141.70	$141.70
Purchase #5	$73.96	3.303%	$76.4029	$76.40	$76.40	$76.40
Purchase #6	$135.60	4.764%	$142.06	$142.06	$142.05	$142.10
Purchase #7	$167.48	5.165%	$176.1303	$176.13	$176.15	$176.10
7 purchase totals =	$904.04		$946.3935	$946.39	$946.40	$946.40