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	$173.43	6.767%	$185.166	$185.17	$185.15	$185.20
Purchase #2	$87.42	4.749%	$91.5716	$91.57	$91.55	$91.60
Purchase #3	$177.94	5.798%	$188.257	$188.26	$188.25	$188.30
Purchase #4	$179.98	4.270%	$187.6651	$187.67	$187.65	$187.70
Purchase #5	$100.36	12.123%	$112.5266	$112.53	$112.55	$112.50
Purchase #6	$129.44	7.806%	$139.5441	$139.54	$139.55	$139.50
Purchase #7	$126.44	3.808%	$131.2548	$131.25	$131.25	$131.30
7 purchase totals =	$975.01		$1,035.9852	$1,035.99	$1,035.95	$1,036.10