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	$69.48	6.864%	$74.2491	$74.25	$74.25	$74.20
Purchase #2	$90.61	9.172%	$98.9207	$98.92	$98.90	$98.90
Purchase #3	$142.39	11.754%	$159.1265	$159.13	$159.15	$159.10
Purchase #4	$164.37	5.772%	$173.8574	$173.86	$173.85	$173.90
Purchase #5	$41.82	9.234%	$45.6817	$45.68	$45.70	$45.70
Purchase #6	$156.50	9.543%	$171.4348	$171.43	$171.45	$171.40
Purchase #7	$163.37	11.120%	$181.5367	$181.54	$181.55	$181.50
7 purchase totals =	$828.54		$904.8069	$904.81	$904.85	$904.70