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	$109.36	13.350%	$123.9596	$123.96	$123.95	$124.00
Purchase #2	$153.39	7.756%	$165.2869	$165.29	$165.30	$165.30
Purchase #3	$165.79	12.709%	$186.8603	$186.86	$186.85	$186.90
Purchase #4	$198.38	6.613%	$211.4989	$211.50	$211.50	$211.50
Purchase #5	$53.71	12.724%	$60.5441	$60.54	$60.55	$60.50
Purchase #6	$178.96	4.852%	$187.6431	$187.64	$187.65	$187.60
Purchase #7	$136.72	8.745%	$148.6762	$148.68	$148.70	$148.70
7 purchase totals =	$996.31		$1,084.4691	$1,084.47	$1,084.50	$1,084.50