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	$164.66	6.502%	$175.3662	$175.37	$175.35	$175.40
Purchase #2	$136.44	13.466%	$154.813	$154.81	$154.80	$154.80
Purchase #3	$166.68	8.742%	$181.2512	$181.25	$181.25	$181.30
Purchase #4	$10.90	3.811%	$11.3154	$11.32	$11.30	$11.30
Purchase #5	$83.46	7.707%	$89.8923	$89.89	$89.90	$89.90
Purchase #6	$157.61	9.851%	$173.1362	$173.14	$173.15	$173.10
Purchase #7	$162.52	5.571%	$171.574	$171.57	$171.55	$171.60
7 purchase totals =	$882.27		$957.3483	$957.35	$957.30	$957.40