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	$177.59	4.525%	$185.6259	$185.63	$185.65	$185.60
Purchase #2	$154.61	10.665%	$171.0992	$171.10	$171.10	$171.10
Purchase #3	$105.35	11.539%	$117.5063	$117.51	$117.50	$117.50
Purchase #4	$95.52	10.598%	$105.6432	$105.64	$105.65	$105.60
Purchase #5	$55.30	4.846%	$57.9798	$57.98	$58.00	$58.00
Purchase #6	$181.41	10.511%	$200.478	$200.48	$200.50	$200.50
Purchase #7	$132.28	11.441%	$147.4142	$147.41	$147.40	$147.40
7 purchase totals =	$902.06		$985.7466	$985.75	$985.80	$985.70