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	$76.77	11.218%	$85.3821	$85.38	$85.40	$85.40
Purchase #2	$228.76	5.490%	$241.3189	$241.32	$241.30	$241.30
Purchase #3	$141.56	4.871%	$148.4554	$148.46	$148.45	$148.50
Purchase #4	$49.92	3.576%	$51.7051	$51.71	$51.70	$51.70
Purchase #5	$204.84	12.102%	$229.6297	$229.63	$229.65	$229.60
Purchase #6	$250.56	10.412%	$276.6483	$276.65	$276.65	$276.60
Purchase #7	$25.79	10.117%	$28.3992	$28.40	$28.40	$28.40
7 purchase totals =	$978.20		$1,061.5387	$1,061.55	$1,061.55	$1,061.50