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	$86.84	3.244%	$89.6571	$89.66	$89.65	$89.70
Purchase #2	$166.26	13.232%	$188.2595	$188.26	$188.25	$188.30
Purchase #3	$198.95	11.479%	$221.7875	$221.79	$221.80	$221.80
Purchase #4	$228.49	5.691%	$241.4934	$241.49	$241.50	$241.50
Purchase #5	$42.45	11.599%	$47.3738	$47.37	$47.35	$47.40
Purchase #6	$160.64	4.128%	$167.2712	$167.27	$167.25	$167.30
Purchase #7	$142.85	13.505%	$162.1419	$162.14	$162.15	$162.10
7 purchase totals =	$1,026.48		$1,117.9844	$1,117.98	$1,117.95	$1,118.10