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	$110.95	7.577%	$119.3567	$119.36	$119.35	$119.40
Purchase #2	$93.93	6.729%	$100.2505	$100.25	$100.25	$100.30
Purchase #3	$118.89	3.713%	$123.3044	$123.30	$123.30	$123.30
Purchase #4	$202.53	5.820%	$214.3172	$214.32	$214.30	$214.30
Purchase #5	$105.30	5.655%	$111.2547	$111.25	$111.25	$111.30
Purchase #6	$132.90	10.842%	$147.309	$147.31	$147.30	$147.30
Purchase #7	$114.62	12.645%	$129.1137	$129.11	$129.10	$129.10
7 purchase totals =	$879.12		$944.9062	$944.90	$944.85	$945.00