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	$91.66	8.366%	$99.3283	$99.33	$99.35	$99.30
Purchase #2	$152.29	13.283%	$172.5187	$172.52	$172.50	$172.50
Purchase #3	$43.74	7.467%	$47.0061	$47.01	$47.00	$47.00
Purchase #4	$192.88	6.745%	$205.8898	$205.89	$205.90	$205.90
Purchase #5	$187.67	10.106%	$206.6359	$206.64	$206.65	$206.60
Purchase #6	$235.65	8.869%	$256.5498	$256.55	$256.55	$256.50
Purchase #7	$82.79	10.843%	$91.7669	$91.77	$91.75	$91.80
7 purchase totals =	$986.68		$1,079.6955	$1,079.71	$1,079.70	$1,079.60