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	$213.79	8.436%	$231.8253	$231.83	$231.85	$231.80
Purchase #2	$194.32	8.653%	$211.1345	$211.13	$211.15	$211.10
Purchase #3	$190.42	3.349%	$196.7972	$196.80	$196.80	$196.80
Purchase #4	$57.36	12.159%	$64.3344	$64.33	$64.35	$64.30
Purchase #5	$118.30	8.303%	$128.1224	$128.12	$128.10	$128.10
Purchase #6	$242.38	11.320%	$269.8174	$269.82	$269.80	$269.80
Purchase #7	$27.64	4.262%	$28.818	$28.82	$28.80	$28.80
7 purchase totals =	$1,044.21		$1,130.8492	$1,130.85	$1,130.85	$1,130.70