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	$186.47	5.256%	$196.2709	$196.27	$196.25	$196.30
Purchase #2	$223.87	7.215%	$240.0222	$240.02	$240.00	$240.00
Purchase #3	$81.69	9.655%	$89.5772	$89.58	$89.60	$89.60
Purchase #4	$156.56	10.634%	$173.2086	$173.21	$173.20	$173.20
Purchase #5	$171.69	4.201%	$178.9027	$178.90	$178.90	$178.90
Purchase #6	$165.54	12.459%	$186.1646	$186.16	$186.15	$186.20
Purchase #7	$176.34	3.454%	$182.4308	$182.43	$182.45	$182.40
7 purchase totals =	$1,162.16		$1,246.5770	$1,246.57	$1,246.55	$1,246.60