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	$154.73	11.436%	$172.4249	$172.42	$172.40	$172.40
Purchase #2	$164.37	10.791%	$182.1072	$182.11	$182.10	$182.10
Purchase #3	$225.44	7.692%	$242.7808	$242.78	$242.80	$242.80
Purchase #4	$65.50	3.171%	$67.577	$67.58	$67.60	$67.60
Purchase #5	$189.33	11.583%	$211.2601	$211.26	$211.25	$211.30
Purchase #6	$33.98	12.649%	$38.2781	$38.28	$38.30	$38.30
Purchase #7	$76.40	11.780%	$85.3999	$85.40	$85.40	$85.40
7 purchase totals =	$909.75		$999.8280	$999.83	$999.85	$999.90