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	$180.97	6.387%	$192.5286	$192.53	$192.55	$192.50
Purchase #2	$52.81	5.277%	$55.5968	$55.60	$55.60	$55.60
Purchase #3	$243.59	11.303%	$271.123	$271.12	$271.10	$271.10
Purchase #4	$60.87	7.857%	$65.6526	$65.65	$65.65	$65.70
Purchase #5	$17.87	6.783%	$19.0821	$19.08	$19.10	$19.10
Purchase #6	$250.67	7.130%	$268.5428	$268.54	$268.55	$268.50
Purchase #7	$225.67	5.826%	$238.8175	$238.82	$238.80	$238.80
7 purchase totals =	$1,032.45		$1,111.3434	$1,111.34	$1,111.35	$1,111.30