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	$60.36	8.460%	$65.4665	$65.47	$65.45	$65.50
Purchase #2	$121.88	3.577%	$126.2396	$126.24	$126.25	$126.20
Purchase #3	$136.44	6.616%	$145.4669	$145.47	$145.45	$145.50
Purchase #4	$54.61	7.228%	$58.5572	$58.56	$58.55	$58.60
Purchase #5	$170.89	10.531%	$188.8864	$188.89	$188.90	$188.90
Purchase #6	$90.89	12.751%	$102.4794	$102.48	$102.50	$102.50
Purchase #7	$225.43	10.183%	$248.3855	$248.39	$248.40	$248.40
7 purchase totals =	$860.50		$935.4815	$935.50	$935.50	$935.60