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	$230.94	3.494%	$239.009	$239.01	$239.00	$239.00
Purchase #2	$55.65	6.671%	$59.3624	$59.36	$59.35	$59.40
Purchase #3	$91.49	8.360%	$99.1386	$99.14	$99.15	$99.10
Purchase #4	$222.36	13.251%	$251.8249	$251.82	$251.80	$251.80
Purchase #5	$45.62	9.562%	$49.9822	$49.98	$50.00	$50.00
Purchase #6	$122.75	11.542%	$136.9178	$136.92	$136.90	$136.90
Purchase #7	$169.72	12.151%	$190.3427	$190.34	$190.35	$190.30
7 purchase totals =	$938.53		$1,026.5776	$1,026.57	$1,026.55	$1,026.50