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	$50.77	10.457%	$56.079	$56.08	$56.10	$56.10
Purchase #2	$250.38	4.739%	$262.2455	$262.25	$262.25	$262.20
Purchase #3	$84.30	13.416%	$95.6097	$95.61	$95.60	$95.60
Purchase #4	$75.94	8.641%	$82.502	$82.50	$82.50	$82.50
Purchase #5	$55.41	6.623%	$59.0798	$59.08	$59.10	$59.10
Purchase #6	$218.44	11.578%	$243.731	$243.73	$243.75	$243.70
Purchase #7	$89.65	13.734%	$101.9625	$101.96	$101.95	$102.00
7 purchase totals =	$824.89		$901.2095	$901.21	$901.25	$901.20