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	$80.57	13.330%	$91.31	$91.31	$91.30	$91.30
Purchase #2	$107.58	3.640%	$111.4959	$111.50	$111.50	$111.50
Purchase #3	$215.34	5.850%	$227.9374	$227.94	$227.95	$227.90
Purchase #4	$149.69	8.518%	$162.4406	$162.44	$162.45	$162.40
Purchase #5	$108.47	5.352%	$114.2753	$114.28	$114.30	$114.30
Purchase #6	$222.55	4.359%	$232.251	$232.25	$232.25	$232.30
Purchase #7	$138.84	12.544%	$156.2561	$156.26	$156.25	$156.30
7 purchase totals =	$1,023.04		$1,095.9663	$1,095.98	$1,096.00	$1,096.00