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	$233.73	10.725%	$258.7975	$258.80	$258.80	$258.80
Purchase #2	$63.76	11.853%	$71.3175	$71.32	$71.30	$71.30
Purchase #3	$149.73	6.209%	$159.0267	$159.03	$159.05	$159.00
Purchase #4	$117.81	9.705%	$129.2435	$129.24	$129.25	$129.20
Purchase #5	$230.67	10.158%	$254.1015	$254.10	$254.10	$254.10
Purchase #6	$64.81	4.742%	$67.8833	$67.88	$67.90	$67.90
Purchase #7	$151.78	8.601%	$164.8346	$164.83	$164.85	$164.80
7 purchase totals =	$1,012.29		$1,105.2046	$1,105.20	$1,105.25	$1,105.10