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	$52.52	4.349%	$54.8041	$54.80	$54.80	$54.80
Purchase #2	$156.27	5.633%	$165.0727	$165.07	$165.05	$165.10
Purchase #3	$89.62	9.423%	$98.0649	$98.06	$98.05	$98.10
Purchase #4	$209.53	10.250%	$231.0068	$231.01	$231.00	$231.00
Purchase #5	$216.83	11.185%	$241.0824	$241.08	$241.10	$241.10
Purchase #6	$184.57	3.812%	$191.6058	$191.61	$191.60	$191.60
Purchase #7	$247.59	10.719%	$274.1292	$274.13	$274.15	$274.10
7 purchase totals =	$1,156.93		$1,255.7659	$1,255.76	$1,255.75	$1,255.80