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	$200.49	9.449%	$219.4343	$219.43	$219.45	$219.40
Purchase #2	$41.78	12.104%	$46.8371	$46.84	$46.85	$46.80
Purchase #3	$211.33	8.602%	$229.5086	$229.51	$229.50	$229.50
Purchase #4	$206.47	10.731%	$228.6263	$228.63	$228.65	$228.60
Purchase #5	$162.26	6.146%	$172.2325	$172.23	$172.25	$172.20
Purchase #6	$123.76	3.869%	$128.5483	$128.55	$128.55	$128.50
Purchase #7	$31.78	9.829%	$34.9037	$34.90	$34.90	$34.90
7 purchase totals =	$977.87		$1,060.0908	$1,060.09	$1,060.15	$1,059.90