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	$200.28	11.805%	$223.9231	$223.92	$223.90	$223.90
Purchase #2	$64.90	11.102%	$72.1052	$72.11	$72.10	$72.10
Purchase #3	$225.81	5.154%	$237.4482	$237.45	$237.45	$237.40
Purchase #4	$227.49	11.353%	$253.3169	$253.32	$253.30	$253.30
Purchase #5	$41.67	8.579%	$45.2449	$45.24	$45.25	$45.20
Purchase #6	$238.31	11.618%	$265.9969	$266.00	$266.00	$266.00
Purchase #7	$82.76	4.286%	$86.3071	$86.31	$86.30	$86.30
7 purchase totals =	$1,081.22		$1,184.3423	$1,184.35	$1,184.30	$1,184.20