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	$68.88	13.396%	$78.1072	$78.11	$78.10	$78.10
Purchase #2	$165.40	8.722%	$179.8262	$179.83	$179.85	$179.80
Purchase #3	$235.27	11.722%	$262.8483	$262.85	$262.85	$262.80
Purchase #4	$239.92	3.202%	$247.6022	$247.60	$247.60	$247.60
Purchase #5	$159.87	5.626%	$168.8643	$168.86	$168.85	$168.90
Purchase #6	$144.59	4.132%	$150.5645	$150.56	$150.55	$150.60
Purchase #7	$32.25	13.306%	$36.5412	$36.54	$36.55	$36.50
7 purchase totals =	$1,046.18		$1,124.3539	$1,124.35	$1,124.35	$1,124.30