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	$191.73	3.863%	$199.1365	$199.14	$199.15	$199.10
Purchase #2	$71.88	9.800%	$78.9242	$78.92	$78.90	$78.90
Purchase #3	$132.36	6.112%	$140.4498	$140.45	$140.45	$140.40
Purchase #4	$156.56	10.462%	$172.9393	$172.94	$172.95	$172.90
Purchase #5	$100.33	5.795%	$106.1441	$106.14	$106.15	$106.10
Purchase #6	$87.75	10.292%	$96.7812	$96.78	$96.80	$96.80
Purchase #7	$47.29	13.660%	$53.7498	$53.75	$53.75	$53.70
7 purchase totals =	$787.90		$848.1249	$848.12	$848.15	$847.90