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	$173.64	4.435%	$181.3409	$181.34	$181.35	$181.30
Purchase #2	$203.89	6.580%	$217.306	$217.31	$217.30	$217.30
Purchase #3	$210.49	5.669%	$222.4227	$222.42	$222.40	$222.40
Purchase #4	$176.86	9.496%	$193.6546	$193.65	$193.65	$193.70
Purchase #5	$89.31	12.563%	$100.53	$100.53	$100.55	$100.50
Purchase #6	$123.64	8.535%	$134.1927	$134.19	$134.20	$134.20
Purchase #7	$112.28	10.330%	$123.8785	$123.88	$123.90	$123.90
7 purchase totals =	$1,090.11		$1,173.3254	$1,173.32	$1,173.35	$1,173.30