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	$109.37	8.675%	$118.8578	$118.86	$118.85	$118.90
Purchase #2	$190.76	7.830%	$205.6965	$205.70	$205.70	$205.70
Purchase #3	$167.59	7.162%	$179.5928	$179.59	$179.60	$179.60
Purchase #4	$249.93	11.582%	$278.8769	$278.88	$278.90	$278.90
Purchase #5	$219.56	12.116%	$246.1619	$246.16	$246.15	$246.20
Purchase #6	$232.55	4.312%	$242.5776	$242.58	$242.60	$242.60
Purchase #7	$133.39	12.825%	$150.4973	$150.50	$150.50	$150.50
7 purchase totals =	$1,303.15		$1,422.2608	$1,422.27	$1,422.30	$1,422.40