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	$149.76	4.217%	$156.0754	$156.08	$156.10	$156.10
Purchase #2	$83.46	5.269%	$87.8575	$87.86	$87.85	$87.90
Purchase #3	$30.87	8.718%	$33.5612	$33.56	$33.55	$33.60
Purchase #4	$78.97	4.803%	$82.7629	$82.76	$82.75	$82.80
Purchase #5	$53.67	6.105%	$56.9466	$56.95	$56.95	$56.90
Purchase #6	$154.48	13.855%	$175.8832	$175.88	$175.90	$175.90
Purchase #7	$229.58	9.241%	$250.7955	$250.80	$250.80	$250.80
7 purchase totals =	$780.79		$843.8823	$843.89	$843.90	$844.00