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	$73.78	3.586%	$76.4258	$76.43	$76.45	$76.40
Purchase #2	$104.76	6.145%	$111.1975	$111.20	$111.20	$111.20
Purchase #3	$242.77	9.132%	$264.9398	$264.94	$264.95	$264.90
Purchase #4	$94.86	9.104%	$103.4961	$103.50	$103.50	$103.50
Purchase #5	$25.47	7.560%	$27.3955	$27.40	$27.40	$27.40
Purchase #6	$206.59	8.842%	$224.8567	$224.86	$224.85	$224.90
Purchase #7	$118.58	8.223%	$128.3308	$128.33	$128.35	$128.30
7 purchase totals =	$866.81		$936.6422	$936.66	$936.70	$936.60