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	$152.44	7.485%	$163.8501	$163.85	$163.85	$163.90
Purchase #2	$52.82	5.432%	$55.6892	$55.69	$55.70	$55.70
Purchase #3	$122.40	5.301%	$128.8884	$128.89	$128.90	$128.90
Purchase #4	$17.59	5.628%	$18.58	$18.58	$18.60	$18.60
Purchase #5	$160.85	6.547%	$171.3808	$171.38	$171.40	$171.40
Purchase #6	$233.47	9.617%	$255.9228	$255.92	$255.90	$255.90
Purchase #7	$41.41	13.869%	$47.1532	$47.15	$47.15	$47.20
7 purchase totals =	$780.98		$841.4645	$841.46	$841.50	$841.60