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	$140.90	10.804%	$156.1228	$156.12	$156.10	$156.10
Purchase #2	$94.69	10.366%	$104.5056	$104.51	$104.50	$104.50
Purchase #3	$168.51	11.415%	$187.7454	$187.75	$187.75	$187.70
Purchase #4	$171.97	7.646%	$185.1188	$185.12	$185.10	$185.10
Purchase #5	$225.28	12.743%	$253.9874	$253.99	$254.00	$254.00
Purchase #6	$67.68	7.778%	$72.9442	$72.94	$72.95	$72.90
Purchase #7	$111.88	8.710%	$121.6247	$121.62	$121.60	$121.60
7 purchase totals =	$980.91		$1,082.0489	$1,082.05	$1,082.00	$1,081.90