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	$63.98	12.615%	$72.0511	$72.05	$72.05	$72.10
Purchase #2	$86.69	5.306%	$91.2898	$91.29	$91.30	$91.30
Purchase #3	$171.85	6.214%	$182.5288	$182.53	$182.55	$182.50
Purchase #4	$161.71	4.234%	$168.5568	$168.56	$168.55	$168.60
Purchase #5	$47.29	8.144%	$51.1413	$51.14	$51.15	$51.10
Purchase #6	$210.52	7.416%	$226.1322	$226.13	$226.15	$226.10
Purchase #7	$88.69	11.311%	$98.7217	$98.72	$98.70	$98.70
7 purchase totals =	$830.73		$890.4217	$890.42	$890.45	$890.40