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	$33.50	4.725%	$35.0829	$35.08	$35.10	$35.10
Purchase #2	$170.46	5.148%	$179.2353	$179.24	$179.25	$179.20
Purchase #3	$148.35	5.451%	$156.4366	$156.44	$156.45	$156.40
Purchase #4	$203.66	13.107%	$230.3537	$230.35	$230.35	$230.40
Purchase #5	$116.38	12.558%	$130.995	$131.00	$131.00	$131.00
Purchase #6	$78.86	8.139%	$85.2784	$85.28	$85.30	$85.30
Purchase #7	$204.51	9.231%	$223.3883	$223.39	$223.40	$223.40
7 purchase totals =	$955.72		$1,040.7702	$1,040.78	$1,040.85	$1,040.80