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	$198.65	12.296%	$223.076	$223.08	$223.10	$223.10
Purchase #2	$101.59	3.184%	$104.8246	$104.82	$104.80	$104.80
Purchase #3	$16.81	11.281%	$18.7063	$18.71	$18.70	$18.70
Purchase #4	$184.64	11.429%	$205.7425	$205.74	$205.75	$205.70
Purchase #5	$177.60	7.479%	$190.8827	$190.88	$190.90	$190.90
Purchase #6	$102.79	6.146%	$109.1075	$109.11	$109.10	$109.10
Purchase #7	$225.52	3.574%	$233.5801	$233.58	$233.60	$233.60
7 purchase totals =	$1,007.60		$1,085.9197	$1,085.92	$1,085.95	$1,085.90