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	$166.34	9.369%	$181.9244	$181.92	$181.90	$181.90
Purchase #2	$18.82	5.800%	$19.9116	$19.91	$19.90	$19.90
Purchase #3	$213.32	4.215%	$222.3114	$222.31	$222.30	$222.30
Purchase #4	$107.54	13.721%	$122.2956	$122.30	$122.30	$122.30
Purchase #5	$241.90	9.757%	$265.5022	$265.50	$265.50	$265.50
Purchase #6	$132.47	12.131%	$148.5399	$148.54	$148.55	$148.50
Purchase #7	$82.39	12.580%	$92.7547	$92.75	$92.75	$92.80
7 purchase totals =	$962.78		$1,053.2398	$1,053.23	$1,053.20	$1,053.20