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	$182.79	6.259%	$194.2308	$194.23	$194.25	$194.20
Purchase #2	$84.54	9.281%	$92.3862	$92.39	$92.40	$92.40
Purchase #3	$170.39	12.327%	$191.394	$191.39	$191.40	$191.40
Purchase #4	$230.88	8.635%	$250.8165	$250.82	$250.80	$250.80
Purchase #5	$46.39	9.539%	$50.8151	$50.82	$50.80	$50.80
Purchase #6	$161.47	4.210%	$168.2679	$168.27	$168.25	$168.30
Purchase #7	$41.25	5.661%	$43.5852	$43.59	$43.60	$43.60
7 purchase totals =	$917.71		$991.4957	$991.51	$991.50	$991.50