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	$157.78	9.551%	$172.8496	$172.85	$172.85	$172.80
Purchase #2	$117.39	9.112%	$128.0866	$128.09	$128.10	$128.10
Purchase #3	$95.84	4.249%	$99.9122	$99.91	$99.90	$99.90
Purchase #4	$179.84	10.298%	$198.3599	$198.36	$198.35	$198.40
Purchase #5	$130.66	5.152%	$137.3916	$137.39	$137.40	$137.40
Purchase #6	$188.33	4.104%	$196.0591	$196.06	$196.05	$196.10
Purchase #7	$216.34	4.164%	$225.3484	$225.35	$225.35	$225.30
7 purchase totals =	$1,086.18		$1,158.0074	$1,158.01	$1,158.00	$1,158.00