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	$159.80	5.356%	$168.3589	$168.36	$168.35	$168.40
Purchase #2	$143.45	6.226%	$152.3812	$152.38	$152.40	$152.40
Purchase #3	$36.50	11.829%	$40.8176	$40.82	$40.80	$40.80
Purchase #4	$230.33	11.775%	$257.4514	$257.45	$257.45	$257.50
Purchase #5	$238.98	9.833%	$262.4789	$262.48	$262.50	$262.50
Purchase #6	$53.40	3.399%	$55.2151	$55.22	$55.20	$55.20
Purchase #7	$82.69	10.576%	$91.4353	$91.44	$91.45	$91.40
7 purchase totals =	$945.15		$1,028.1384	$1,028.15	$1,028.15	$1,028.20