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	$165.32	12.422%	$185.8561	$185.86	$185.85	$185.90
Purchase #2	$157.36	7.168%	$168.6396	$168.64	$168.65	$168.60
Purchase #3	$61.64	11.792%	$68.9086	$68.91	$68.90	$68.90
Purchase #4	$67.35	7.172%	$72.1803	$72.18	$72.20	$72.20
Purchase #5	$199.42	10.665%	$220.6881	$220.69	$220.70	$220.70
Purchase #6	$200.47	11.131%	$222.7843	$222.78	$222.80	$222.80
Purchase #7	$198.84	13.185%	$225.0571	$225.06	$225.05	$225.10
7 purchase totals =	$1,050.40		$1,164.1141	$1,164.12	$1,164.15	$1,164.20