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	$206.47	6.470%	$219.8286	$219.83	$219.85	$219.80
Purchase #2	$224.87	4.754%	$235.5603	$235.56	$235.55	$235.60
Purchase #3	$103.39	9.252%	$112.9556	$112.96	$112.95	$113.00
Purchase #4	$238.84	6.872%	$255.2531	$255.25	$255.25	$255.30
Purchase #5	$73.32	10.532%	$81.0421	$81.04	$81.05	$81.00
Purchase #6	$137.78	7.763%	$148.4759	$148.48	$148.50	$148.50
Purchase #7	$89.90	10.172%	$99.0446	$99.04	$99.05	$99.00
7 purchase totals =	$1,074.57		$1,152.1602	$1,152.16	$1,152.20	$1,152.20