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	$246.52	7.207%	$264.2867	$264.29	$264.30	$264.30
Purchase #2	$233.28	7.490%	$250.7527	$250.75	$250.75	$250.80
Purchase #3	$143.98	8.269%	$155.8857	$155.89	$155.90	$155.90
Purchase #4	$118.40	13.400%	$134.2656	$134.27	$134.25	$134.30
Purchase #5	$39.31	3.464%	$40.6717	$40.67	$40.65	$40.70
Purchase #6	$162.36	10.711%	$179.7504	$179.75	$179.75	$179.80
Purchase #7	$72.93	8.176%	$78.8928	$78.89	$78.90	$78.90
7 purchase totals =	$1,016.78		$1,104.5056	$1,104.51	$1,104.50	$1,104.70