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	$174.32	9.767%	$191.3458	$191.35	$191.35	$191.30
Purchase #2	$28.25	10.715%	$31.277	$31.28	$31.30	$31.30
Purchase #3	$209.99	6.259%	$223.1333	$223.13	$223.15	$223.10
Purchase #4	$49.72	4.741%	$52.0772	$52.08	$52.10	$52.10
Purchase #5	$59.41	11.819%	$66.4317	$66.43	$66.45	$66.40
Purchase #6	$9.66	13.125%	$10.9279	$10.93	$10.95	$10.90
Purchase #7	$198.37	12.693%	$223.5491	$223.55	$223.55	$223.50
7 purchase totals =	$729.72		$798.7420	$798.75	$798.85	$798.60