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	$95.54	8.835%	$103.981	$103.98	$104.00	$104.00
Purchase #2	$152.33	3.398%	$157.5062	$157.51	$157.50	$157.50
Purchase #3	$228.68	12.365%	$256.9563	$256.96	$256.95	$257.00
Purchase #4	$205.92	12.412%	$231.4788	$231.48	$231.50	$231.50
Purchase #5	$122.44	13.635%	$139.1347	$139.13	$139.15	$139.10
Purchase #6	$154.69	8.684%	$168.1233	$168.12	$168.10	$168.10
Purchase #7	$30.86	10.107%	$33.979	$33.98	$34.00	$34.00
7 purchase totals =	$990.46		$1,091.1593	$1,091.16	$1,091.20	$1,091.20