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	$45.50	8.505%	$49.3698	$49.37	$49.35	$49.40
Purchase #2	$171.30	6.481%	$182.402	$182.40	$182.40	$182.40
Purchase #3	$196.27	12.457%	$220.7194	$220.72	$220.70	$220.70
Purchase #4	$236.51	11.726%	$264.2432	$264.24	$264.25	$264.20
Purchase #5	$134.81	7.556%	$144.9962	$145.00	$145.00	$145.00
Purchase #6	$165.48	11.856%	$185.0993	$185.10	$185.10	$185.10
Purchase #7	$37.68	13.381%	$42.722	$42.72	$42.70	$42.70
7 purchase totals =	$987.55		$1,089.5519	$1,089.55	$1,089.50	$1,089.50