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	$37.95	8.367%	$41.1253	$41.13	$41.15	$41.10
Purchase #2	$21.99	5.742%	$23.2527	$23.25	$23.25	$23.30
Purchase #3	$101.66	10.758%	$112.5966	$112.60	$112.60	$112.60
Purchase #4	$78.41	9.833%	$86.1201	$86.12	$86.10	$86.10
Purchase #5	$109.72	10.144%	$120.85	$120.85	$120.85	$120.90
Purchase #6	$168.58	6.114%	$178.887	$178.89	$178.90	$178.90
Purchase #7	$78.39	13.573%	$89.0299	$89.03	$89.05	$89.00
7 purchase totals =	$596.70		$651.8616	$651.87	$651.90	$651.90