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	$99.54	10.226%	$109.719	$109.72	$109.70	$109.70
Purchase #2	$38.46	7.607%	$41.3857	$41.39	$41.40	$41.40
Purchase #3	$216.94	10.714%	$240.183	$240.18	$240.20	$240.20
Purchase #4	$219.40	3.762%	$227.6538	$227.65	$227.65	$227.70
Purchase #5	$31.81	3.801%	$33.0191	$33.02	$33.00	$33.00
Purchase #6	$194.89	12.668%	$219.5787	$219.58	$219.60	$219.60
Purchase #7	$85.66	5.842%	$90.6643	$90.66	$90.65	$90.70
7 purchase totals =	$886.70		$962.2036	$962.20	$962.20	$962.30