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	$201.32	11.243%	$223.9544	$223.95	$223.95	$224.00
Purchase #2	$91.79	6.476%	$97.7343	$97.73	$97.75	$97.70
Purchase #3	$187.81	6.865%	$200.7032	$200.70	$200.70	$200.70
Purchase #4	$90.33	10.429%	$99.7505	$99.75	$99.75	$99.80
Purchase #5	$19.84	9.201%	$21.6655	$21.67	$21.65	$21.70
Purchase #6	$40.38	13.830%	$45.9646	$45.96	$45.95	$46.00
Purchase #7	$109.81	9.147%	$119.8543	$119.85	$119.85	$119.90
7 purchase totals =	$741.28		$809.6268	$809.61	$809.60	$809.80