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	$80.90	5.179%	$85.0898	$85.09	$85.10	$85.10
Purchase #2	$205.65	13.549%	$233.5135	$233.51	$233.50	$233.50
Purchase #3	$200.86	5.508%	$211.9234	$211.92	$211.90	$211.90
Purchase #4	$51.78	6.472%	$55.1312	$55.13	$55.15	$55.10
Purchase #5	$68.55	11.787%	$76.63	$76.63	$76.65	$76.60
Purchase #6	$242.84	3.461%	$251.2447	$251.24	$251.25	$251.20
Purchase #7	$133.53	13.326%	$151.3242	$151.32	$151.30	$151.30
7 purchase totals =	$984.11		$1,064.8568	$1,064.84	$1,064.85	$1,064.70