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	$222.79	6.158%	$236.5094	$236.51	$236.50	$236.50
Purchase #2	$28.58	12.765%	$32.2282	$32.23	$32.25	$32.20
Purchase #3	$183.65	6.797%	$196.1327	$196.13	$196.15	$196.10
Purchase #4	$82.47	4.789%	$86.4195	$86.42	$86.40	$86.40
Purchase #5	$226.64	12.120%	$254.1088	$254.11	$254.10	$254.10
Purchase #6	$93.25	7.155%	$99.922	$99.92	$99.90	$99.90
Purchase #7	$123.97	11.571%	$138.3146	$138.31	$138.30	$138.30
7 purchase totals =	$961.35		$1,043.6352	$1,043.63	$1,043.60	$1,043.50