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	$152.39	12.611%	$171.6079	$171.61	$171.60	$171.60
Purchase #2	$25.72	4.395%	$26.8504	$26.85	$26.85	$26.90
Purchase #3	$220.73	6.147%	$234.2983	$234.30	$234.30	$234.30
Purchase #4	$81.54	4.501%	$85.2101	$85.21	$85.20	$85.20
Purchase #5	$184.47	6.736%	$196.8959	$196.90	$196.90	$196.90
Purchase #6	$212.48	8.638%	$230.834	$230.83	$230.85	$230.80
Purchase #7	$82.81	9.402%	$90.5958	$90.60	$90.60	$90.60
7 purchase totals =	$960.14		$1,036.2924	$1,036.30	$1,036.30	$1,036.30