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	$86.48	5.438%	$91.1828	$91.18	$91.20	$91.20
Purchase #2	$17.49	6.317%	$18.5948	$18.59	$18.60	$18.60
Purchase #3	$176.72	7.254%	$189.5393	$189.54	$189.55	$189.50
Purchase #4	$137.91	7.662%	$148.4767	$148.48	$148.50	$148.50
Purchase #5	$70.33	8.763%	$76.493	$76.49	$76.50	$76.50
Purchase #6	$38.83	7.769%	$41.8467	$41.85	$41.85	$41.80
Purchase #7	$162.59	3.425%	$168.1587	$168.16	$168.15	$168.20
7 purchase totals =	$690.35		$734.2920	$734.29	$734.35	$734.30