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	$245.57	4.410%	$256.3996	$256.40	$256.40	$256.40
Purchase #2	$35.56	3.188%	$36.6937	$36.69	$36.70	$36.70
Purchase #3	$171.60	7.189%	$183.9363	$183.94	$183.95	$183.90
Purchase #4	$131.35	4.390%	$137.1163	$137.12	$137.10	$137.10
Purchase #5	$81.86	4.596%	$85.6223	$85.62	$85.60	$85.60
Purchase #6	$171.73	6.425%	$182.7637	$182.76	$182.75	$182.80
Purchase #7	$105.48	5.813%	$111.6116	$111.61	$111.60	$111.60
7 purchase totals =	$943.15		$994.1435	$994.14	$994.10	$994.10