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	$207.93	6.361%	$221.1564	$221.16	$221.15	$221.20
Purchase #2	$95.68	5.181%	$100.6372	$100.64	$100.65	$100.60
Purchase #3	$47.62	9.373%	$52.0834	$52.08	$52.10	$52.10
Purchase #4	$36.62	6.412%	$38.9681	$38.97	$38.95	$39.00
Purchase #5	$72.98	7.749%	$78.6352	$78.64	$78.65	$78.60
Purchase #6	$150.90	6.115%	$160.1275	$160.13	$160.15	$160.10
Purchase #7	$48.63	11.751%	$54.3445	$54.34	$54.35	$54.30
7 purchase totals =	$660.36		$705.9523	$705.96	$706.00	$705.90