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	$239.53	10.598%	$264.9154	$264.92	$264.90	$264.90
Purchase #2	$245.82	13.741%	$279.5981	$279.60	$279.60	$279.60
Purchase #3	$186.44	5.184%	$196.105	$196.11	$196.10	$196.10
Purchase #4	$221.50	5.756%	$234.2495	$234.25	$234.25	$234.20
Purchase #5	$165.91	5.355%	$174.7945	$174.79	$174.80	$174.80
Purchase #6	$153.69	7.359%	$165	$165.00	$165.00	$165.00
Purchase #7	$177.96	10.454%	$196.5639	$196.56	$196.55	$196.60
7 purchase totals =	$1,390.85		$1,511.2264	$1,511.23	$1,511.20	$1,511.20