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	$117.37	7.251%	$125.8805	$125.88	$125.90	$125.90
Purchase #2	$245.43	12.594%	$276.3395	$276.34	$276.35	$276.30
Purchase #3	$76.91	11.191%	$85.517	$85.52	$85.50	$85.50
Purchase #4	$107.33	3.661%	$111.2594	$111.26	$111.25	$111.30
Purchase #5	$84.43	10.112%	$92.9676	$92.97	$92.95	$93.00
Purchase #6	$126.70	4.547%	$132.461	$132.46	$132.45	$132.50
Purchase #7	$249.83	12.118%	$280.1044	$280.10	$280.10	$280.10
7 purchase totals =	$1,008.00		$1,104.5294	$1,104.53	$1,104.50	$1,104.60