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	$150.51	4.201%	$156.8329	$156.83	$156.85	$156.80
Purchase #2	$22.41	12.551%	$25.2227	$25.22	$25.20	$25.20
Purchase #3	$209.83	3.214%	$216.5739	$216.57	$216.55	$216.60
Purchase #4	$80.56	12.864%	$90.9232	$90.92	$90.90	$90.90
Purchase #5	$84.51	10.864%	$93.6912	$93.69	$93.70	$93.70
Purchase #6	$159.30	5.872%	$168.6541	$168.65	$168.65	$168.70
Purchase #7	$56.33	3.709%	$58.4193	$58.42	$58.40	$58.40
7 purchase totals =	$763.45		$810.3173	$810.30	$810.25	$810.30