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	$169.62	7.236%	$181.8937	$181.89	$181.90	$181.90
Purchase #2	$126.73	8.242%	$137.1751	$137.18	$137.20	$137.20
Purchase #3	$130.47	9.232%	$142.515	$142.52	$142.50	$142.50
Purchase #4	$16.36	4.205%	$17.0479	$17.05	$17.05	$17.00
Purchase #5	$57.40	13.725%	$65.2782	$65.28	$65.30	$65.30
Purchase #6	$115.83	6.581%	$123.4528	$123.45	$123.45	$123.50
Purchase #7	$64.59	11.218%	$71.8357	$71.84	$71.85	$71.80
7 purchase totals =	$681.00		$739.1984	$739.21	$739.25	$739.20