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	$81.40	12.717%	$91.7516	$91.75	$91.75	$91.80
Purchase #2	$137.72	4.266%	$143.5951	$143.60	$143.60	$143.60
Purchase #3	$211.61	9.795%	$232.3372	$232.34	$232.35	$232.30
Purchase #4	$78.57	4.480%	$82.0899	$82.09	$82.10	$82.10
Purchase #5	$118.32	11.515%	$131.9445	$131.94	$131.95	$131.90
Purchase #6	$198.83	11.662%	$222.0176	$222.02	$222.00	$222.00
Purchase #7	$196.76	8.110%	$212.7172	$212.72	$212.70	$212.70
7 purchase totals =	$1,023.21		$1,116.4531	$1,116.46	$1,116.45	$1,116.40