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	$168.95	6.746%	$180.3474	$180.35	$180.35	$180.30
Purchase #2	$76.49	7.198%	$81.9958	$82.00	$82.00	$82.00
Purchase #3	$200.35	13.761%	$227.9202	$227.92	$227.90	$227.90
Purchase #4	$98.78	6.791%	$105.4881	$105.49	$105.50	$105.50
Purchase #5	$156.85	9.419%	$171.6237	$171.62	$171.60	$171.60
Purchase #6	$172.68	5.243%	$181.7336	$181.73	$181.75	$181.70
Purchase #7	$37.78	11.322%	$42.0575	$42.06	$42.05	$42.10
7 purchase totals =	$911.88		$991.1663	$991.17	$991.15	$991.10