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	$38.43	12.754%	$43.3314	$43.33	$43.35	$43.30
Purchase #2	$94.56	6.743%	$100.9362	$100.94	$100.95	$100.90
Purchase #3	$219.89	13.776%	$250.182	$250.18	$250.20	$250.20
Purchase #4	$170.70	8.109%	$184.5421	$184.54	$184.55	$184.50
Purchase #5	$205.86	8.738%	$223.848	$223.85	$223.85	$223.80
Purchase #6	$63.77	10.160%	$70.249	$70.25	$70.25	$70.20
Purchase #7	$47.36	3.672%	$49.0991	$49.10	$49.10	$49.10
7 purchase totals =	$840.57		$922.1878	$922.19	$922.25	$922.00