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	$65.94	11.488%	$73.5152	$73.52	$73.50	$73.50
Purchase #2	$75.48	9.866%	$82.9269	$82.93	$82.95	$82.90
Purchase #3	$137.70	10.524%	$152.1915	$152.19	$152.20	$152.20
Purchase #4	$33.96	6.380%	$36.1266	$36.13	$36.15	$36.10
Purchase #5	$141.41	8.843%	$153.9149	$153.91	$153.90	$153.90
Purchase #6	$209.52	11.585%	$233.7929	$233.79	$233.80	$233.80
Purchase #7	$204.26	9.570%	$223.8077	$223.81	$223.80	$223.80
7 purchase totals =	$868.27		$956.2757	$956.28	$956.30	$956.20