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	$170.37	3.128%	$175.6992	$175.70	$175.70	$175.70
Purchase #2	$246.80	13.837%	$280.9497	$280.95	$280.95	$280.90
Purchase #3	$71.31	3.360%	$73.706	$73.71	$73.70	$73.70
Purchase #4	$188.37	6.180%	$200.0113	$200.01	$200.00	$200.00
Purchase #5	$85.87	11.621%	$95.849	$95.85	$95.85	$95.80
Purchase #6	$79.99	6.782%	$85.4149	$85.41	$85.40	$85.40
Purchase #7	$86.75	5.503%	$91.5239	$91.52	$91.50	$91.50
7 purchase totals =	$929.46		$1,003.1540	$1,003.15	$1,003.10	$1,003.00