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	$224.73	11.406%	$250.3627	$250.36	$250.35	$250.40
Purchase #2	$148.81	4.692%	$155.7922	$155.79	$155.80	$155.80
Purchase #3	$7.41	11.802%	$8.2845	$8.28	$8.30	$8.30
Purchase #4	$104.34	9.239%	$113.98	$113.98	$114.00	$114.00
Purchase #5	$187.77	9.386%	$205.3941	$205.39	$205.40	$205.40
Purchase #6	$219.27	6.469%	$233.4546	$233.45	$233.45	$233.50
Purchase #7	$89.39	13.709%	$101.6445	$101.64	$101.65	$101.60
7 purchase totals =	$981.72		$1,068.9126	$1,068.89	$1,068.95	$1,069.00