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	$56.95	12.124%	$63.8546	$63.85	$63.85	$63.90
Purchase #2	$89.27	5.676%	$94.337	$94.34	$94.35	$94.30
Purchase #3	$209.45	9.550%	$229.4525	$229.45	$229.45	$229.50
Purchase #4	$80.28	4.191%	$83.6445	$83.64	$83.65	$83.60
Purchase #5	$118.68	10.771%	$131.463	$131.46	$131.45	$131.50
Purchase #6	$193.93	5.779%	$205.1372	$205.14	$205.15	$205.10
Purchase #7	$71.32	3.133%	$73.5545	$73.55	$73.55	$73.60
7 purchase totals =	$819.88		$881.4433	$881.43	$881.45	$881.50