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	$167.60	6.819%	$179.0286	$179.03	$179.05	$179.00
Purchase #2	$122.53	4.733%	$128.3293	$128.33	$128.35	$128.30
Purchase #3	$229.30	3.834%	$238.0914	$238.09	$238.10	$238.10
Purchase #4	$182.57	7.871%	$196.9401	$196.94	$196.95	$196.90
Purchase #5	$113.54	5.554%	$119.846	$119.85	$119.85	$119.80
Purchase #6	$208.52	10.695%	$230.8212	$230.82	$230.80	$230.80
Purchase #7	$247.73	7.804%	$267.0628	$267.06	$267.05	$267.10
7 purchase totals =	$1,271.79		$1,360.1194	$1,360.12	$1,360.15	$1,360.00