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	$219.74	6.277%	$233.5331	$233.53	$233.55	$233.50
Purchase #2	$28.90	8.418%	$31.3328	$31.33	$31.35	$31.30
Purchase #3	$220.70	4.401%	$230.413	$230.41	$230.40	$230.40
Purchase #4	$91.84	9.859%	$100.8945	$100.89	$100.90	$100.90
Purchase #5	$162.75	11.756%	$181.8829	$181.88	$181.90	$181.90
Purchase #6	$32.97	5.723%	$34.8569	$34.86	$34.85	$34.90
Purchase #7	$40.91	11.850%	$45.7578	$45.76	$45.75	$45.80
7 purchase totals =	$797.81		$858.6710	$858.66	$858.70	$858.70