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	$37.39	11.828%	$41.8125	$41.81	$41.80	$41.80
Purchase #2	$37.52	5.342%	$39.5243	$39.52	$39.50	$39.50
Purchase #3	$86.26	3.765%	$89.5077	$89.51	$89.50	$89.50
Purchase #4	$133.65	10.358%	$147.4935	$147.49	$147.50	$147.50
Purchase #5	$168.27	4.512%	$175.8623	$175.86	$175.85	$175.90
Purchase #6	$83.76	9.510%	$91.7256	$91.73	$91.75	$91.70
Purchase #7	$170.25	3.151%	$175.6146	$175.61	$175.60	$175.60
7 purchase totals =	$717.10		$761.5405	$761.53	$761.50	$761.50