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	$135.28	5.154%	$142.2523	$142.25	$142.25	$142.30
Purchase #2	$160.27	4.217%	$167.0286	$167.03	$167.05	$167.00
Purchase #3	$198.51	6.700%	$211.8102	$211.81	$211.80	$211.80
Purchase #4	$84.66	7.113%	$90.6819	$90.68	$90.70	$90.70
Purchase #5	$7.34	7.515%	$7.8916	$7.89	$7.90	$7.90
Purchase #6	$46.54	8.479%	$50.4861	$50.49	$50.50	$50.50
Purchase #7	$92.55	3.375%	$95.6736	$95.67	$95.65	$95.70
7 purchase totals =	$725.15		$765.8243	$765.82	$765.85	$765.90