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	$59.39	9.807%	$65.2144	$65.21	$65.20	$65.20
Purchase #2	$63.63	6.615%	$67.8391	$67.84	$67.85	$67.80
Purchase #3	$33.71	11.820%	$37.6945	$37.69	$37.70	$37.70
Purchase #4	$167.66	12.295%	$188.2738	$188.27	$188.25	$188.30
Purchase #5	$55.69	3.713%	$57.7578	$57.76	$57.75	$57.80
Purchase #6	$173.31	4.562%	$181.2164	$181.22	$181.20	$181.20
Purchase #7	$202.77	5.298%	$213.5128	$213.51	$213.50	$213.50
7 purchase totals =	$756.16		$811.5088	$811.50	$811.45	$811.50