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	$74.91	10.306%	$82.6302	$82.63	$82.65	$82.60
Purchase #2	$230.85	10.624%	$255.3755	$255.38	$255.40	$255.40
Purchase #3	$76.43	9.111%	$83.3935	$83.39	$83.40	$83.40
Purchase #4	$48.88	4.541%	$51.0996	$51.10	$51.10	$51.10
Purchase #5	$218.91	8.598%	$237.7319	$237.73	$237.75	$237.70
Purchase #6	$192.89	11.672%	$215.4041	$215.40	$215.40	$215.40
Purchase #7	$85.90	6.847%	$91.7816	$91.78	$91.80	$91.80
7 purchase totals =	$928.77		$1,017.4164	$1,017.41	$1,017.50	$1,017.40