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	$233.51	10.461%	$257.9375	$257.94	$257.95	$257.90
Purchase #2	$75.48	4.367%	$78.7762	$78.78	$78.80	$78.80
Purchase #3	$204.56	13.661%	$232.5049	$232.50	$232.50	$232.50
Purchase #4	$64.91	10.559%	$71.7638	$71.76	$71.75	$71.80
Purchase #5	$240.27	7.158%	$257.4685	$257.47	$257.45	$257.50
Purchase #6	$64.81	8.691%	$70.4426	$70.44	$70.45	$70.40
Purchase #7	$186.75	5.219%	$196.4965	$196.50	$196.50	$196.50
7 purchase totals =	$1,070.29		$1,165.3900	$1,165.39	$1,165.40	$1,165.40