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	$36.46	3.792%	$37.8426	$37.84	$37.85	$37.80
Purchase #2	$83.66	13.199%	$94.7023	$94.70	$94.70	$94.70
Purchase #3	$74.45	10.653%	$82.3812	$82.38	$82.40	$82.40
Purchase #4	$152.63	5.430%	$160.9178	$160.92	$160.90	$160.90
Purchase #5	$249.40	6.177%	$264.8054	$264.81	$264.80	$264.80
Purchase #6	$196.60	11.834%	$219.8656	$219.87	$219.85	$219.90
Purchase #7	$77.38	13.181%	$87.5795	$87.58	$87.60	$87.60
7 purchase totals =	$870.58		$948.0944	$948.10	$948.10	$948.10