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	$204.44	9.700%	$224.2707	$224.27	$224.25	$224.30
Purchase #2	$130.59	6.371%	$138.9099	$138.91	$138.90	$138.90
Purchase #3	$204.35	8.388%	$221.4909	$221.49	$221.50	$221.50
Purchase #4	$118.54	11.451%	$132.114	$132.11	$132.10	$132.10
Purchase #5	$193.91	7.786%	$209.0078	$209.01	$209.00	$209.00
Purchase #6	$101.69	8.139%	$109.9665	$109.97	$109.95	$110.00
Purchase #7	$104.51	6.623%	$111.4317	$111.43	$111.45	$111.40
7 purchase totals =	$1,058.03		$1,147.1915	$1,147.19	$1,147.15	$1,147.20