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	$139.96	8.752%	$152.2093	$152.21	$152.20	$152.20
Purchase #2	$86.86	11.170%	$96.5623	$96.56	$96.55	$96.60
Purchase #3	$214.29	5.444%	$225.9559	$225.96	$225.95	$226.00
Purchase #4	$40.69	12.781%	$45.8906	$45.89	$45.90	$45.90
Purchase #5	$48.44	5.608%	$51.1565	$51.16	$51.15	$51.20
Purchase #6	$71.96	8.323%	$77.9492	$77.95	$77.95	$77.90
Purchase #7	$53.94	10.623%	$59.67	$59.67	$59.65	$59.70
7 purchase totals =	$656.14		$709.3938	$709.40	$709.35	$709.50