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	$82.66	10.380%	$91.2401	$91.24	$91.25	$91.20
Purchase #2	$84.36	7.531%	$90.7132	$90.71	$90.70	$90.70
Purchase #3	$196.88	5.258%	$207.232	$207.23	$207.25	$207.20
Purchase #4	$199.82	8.791%	$217.3862	$217.39	$217.40	$217.40
Purchase #5	$55.25	11.486%	$61.596	$61.60	$61.60	$61.60
Purchase #6	$201.88	10.108%	$222.286	$222.29	$222.30	$222.30
Purchase #7	$241.80	4.664%	$253.0776	$253.08	$253.10	$253.10
7 purchase totals =	$1,062.65		$1,143.5311	$1,143.54	$1,143.60	$1,143.50