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	$46.46	5.828%	$49.1677	$49.17	$49.15	$49.20
Purchase #2	$172.63	8.490%	$187.2863	$187.29	$187.30	$187.30
Purchase #3	$161.37	8.335%	$174.8202	$174.82	$174.80	$174.80
Purchase #4	$68.27	13.360%	$77.3909	$77.39	$77.40	$77.40
Purchase #5	$99.86	6.614%	$106.4647	$106.46	$106.45	$106.50
Purchase #6	$138.59	6.804%	$148.0197	$148.02	$148.00	$148.00
Purchase #7	$233.95	9.540%	$256.2688	$256.27	$256.25	$256.30
7 purchase totals =	$921.13		$999.4183	$999.42	$999.35	$999.50