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	$132.38	7.419%	$142.2013	$142.20	$142.20	$142.20
Purchase #2	$194.73	3.185%	$200.9322	$200.93	$200.95	$200.90
Purchase #3	$71.56	4.173%	$74.5462	$74.55	$74.55	$74.50
Purchase #4	$116.54	12.476%	$131.0795	$131.08	$131.10	$131.10
Purchase #5	$110.60	11.685%	$123.5236	$123.52	$123.50	$123.50
Purchase #6	$250.91	8.572%	$272.418	$272.42	$272.40	$272.40
Purchase #7	$243.34	12.278%	$273.2173	$273.22	$273.20	$273.20
7 purchase totals =	$1,120.06		$1,217.9181	$1,217.92	$1,217.90	$1,217.80