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	$79.33	7.547%	$85.317	$85.32	$85.30	$85.30
Purchase #2	$92.79	13.361%	$105.1877	$105.19	$105.20	$105.20
Purchase #3	$174.83	12.585%	$196.8324	$196.83	$196.85	$196.80
Purchase #4	$95.92	7.240%	$102.8646	$102.86	$102.85	$102.90
Purchase #5	$230.60	4.732%	$241.512	$241.51	$241.50	$241.50
Purchase #6	$19.97	13.358%	$22.6376	$22.64	$22.65	$22.60
Purchase #7	$110.57	4.386%	$115.4196	$115.42	$115.40	$115.40
7 purchase totals =	$804.01		$869.7709	$869.77	$869.75	$869.70