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	$89.69	13.708%	$101.9847	$101.98	$102.00	$102.00
Purchase #2	$109.77	11.700%	$122.6131	$122.61	$122.60	$122.60
Purchase #3	$241.76	13.780%	$275.0745	$275.07	$275.05	$275.10
Purchase #4	$111.46	4.756%	$116.761	$116.76	$116.75	$116.80
Purchase #5	$199.27	12.539%	$224.2565	$224.26	$224.25	$224.30
Purchase #6	$97.63	6.397%	$103.8754	$103.88	$103.90	$103.90
Purchase #7	$157.88	6.428%	$168.0285	$168.03	$168.05	$168.00
7 purchase totals =	$1,007.46		$1,112.5937	$1,112.59	$1,112.60	$1,112.70