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	$148.53	8.141%	$160.6218	$160.62	$160.60	$160.60
Purchase #2	$99.37	10.249%	$109.5544	$109.55	$109.55	$109.60
Purchase #3	$200.50	6.112%	$212.7546	$212.75	$212.75	$212.80
Purchase #4	$152.62	4.364%	$159.2803	$159.28	$159.30	$159.30
Purchase #5	$217.59	6.567%	$231.8791	$231.88	$231.90	$231.90
Purchase #6	$7.43	10.731%	$8.2273	$8.23	$8.25	$8.20
Purchase #7	$196.44	10.753%	$217.5632	$217.56	$217.55	$217.60
7 purchase totals =	$1,022.48		$1,099.8807	$1,099.87	$1,099.90	$1,100.00