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	$130.32	3.122%	$134.3886	$134.39	$134.40	$134.40
Purchase #2	$94.74	10.740%	$104.9151	$104.92	$104.90	$104.90
Purchase #3	$166.71	8.858%	$181.4772	$181.48	$181.50	$181.50
Purchase #4	$242.47	10.360%	$267.5899	$267.59	$267.60	$267.60
Purchase #5	$143.35	7.299%	$153.8131	$153.81	$153.80	$153.80
Purchase #6	$137.54	13.530%	$156.1492	$156.15	$156.15	$156.10
Purchase #7	$134.47	7.423%	$144.4517	$144.45	$144.45	$144.50
7 purchase totals =	$1,049.60		$1,142.7848	$1,142.79	$1,142.80	$1,142.80