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	$132.90	4.368%	$138.7051	$138.71	$138.70	$138.70
Purchase #2	$74.70	5.507%	$78.8137	$78.81	$78.80	$78.80
Purchase #3	$173.56	13.283%	$196.614	$196.61	$196.60	$196.60
Purchase #4	$167.72	7.427%	$180.1766	$180.18	$180.20	$180.20
Purchase #5	$167.27	4.650%	$175.0481	$175.05	$175.05	$175.00
Purchase #6	$22.94	11.630%	$25.6079	$25.61	$25.60	$25.60
Purchase #7	$237.94	10.755%	$263.5304	$263.53	$263.55	$263.50
7 purchase totals =	$977.03		$1,058.4958	$1,058.50	$1,058.50	$1,058.40