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	$22.27	13.398%	$25.2537	$25.25	$25.25	$25.30
Purchase #2	$70.96	8.113%	$76.717	$76.72	$76.70	$76.70
Purchase #3	$166.83	11.580%	$186.1489	$186.15	$186.15	$186.10
Purchase #4	$245.44	5.325%	$258.5097	$258.51	$258.50	$258.50
Purchase #5	$164.72	3.757%	$170.9085	$170.91	$170.90	$170.90
Purchase #6	$179.77	9.214%	$196.334	$196.33	$196.35	$196.30
Purchase #7	$165.99	8.524%	$180.139	$180.14	$180.15	$180.10
7 purchase totals =	$1,015.98		$1,094.0108	$1,094.01	$1,094.00	$1,093.90