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	$188.63	9.694%	$206.9158	$206.92	$206.90	$206.90
Purchase #2	$96.54	8.440%	$104.688	$104.69	$104.70	$104.70
Purchase #3	$63.56	6.220%	$67.5134	$67.51	$67.50	$67.50
Purchase #4	$13.66	3.140%	$14.0889	$14.09	$14.10	$14.10
Purchase #5	$103.37	13.690%	$117.5214	$117.52	$117.50	$117.50
Purchase #6	$49.66	3.512%	$51.4041	$51.40	$51.40	$51.40
Purchase #7	$136.35	10.172%	$150.2195	$150.22	$150.20	$150.20
7 purchase totals =	$651.77		$712.3511	$712.35	$712.30	$712.30