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	$69.88	3.259%	$72.1574	$72.16	$72.15	$72.20
Purchase #2	$180.28	3.444%	$186.4888	$186.49	$186.50	$186.50
Purchase #3	$227.92	4.491%	$238.1559	$238.16	$238.15	$238.20
Purchase #4	$64.82	10.421%	$71.5749	$71.57	$71.55	$71.60
Purchase #5	$133.54	11.441%	$148.8183	$148.82	$148.80	$148.80
Purchase #6	$47.94	8.347%	$51.9416	$51.94	$51.95	$51.90
Purchase #7	$37.49	4.626%	$39.2243	$39.22	$39.20	$39.20
7 purchase totals =	$761.87		$808.3612	$808.36	$808.30	$808.40