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	$163.46	3.120%	$168.56	$168.56	$168.55	$168.60
Purchase #2	$188.45	10.103%	$207.4891	$207.49	$207.50	$207.50
Purchase #3	$243.72	4.845%	$255.5282	$255.53	$255.55	$255.50
Purchase #4	$192.95	8.388%	$209.1346	$209.13	$209.15	$209.10
Purchase #5	$50.26	11.550%	$56.065	$56.07	$56.05	$56.10
Purchase #6	$63.72	10.857%	$70.6381	$70.64	$70.65	$70.60
Purchase #7	$85.98	10.372%	$94.8978	$94.90	$94.90	$94.90
7 purchase totals =	$988.54		$1,062.3128	$1,062.32	$1,062.35	$1,062.30