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	$151.35	11.416%	$168.6281	$168.63	$168.65	$168.60
Purchase #2	$78.82	4.752%	$82.5655	$82.57	$82.55	$82.60
Purchase #3	$98.98	5.326%	$104.2517	$104.25	$104.25	$104.30
Purchase #4	$192.32	9.675%	$210.927	$210.93	$210.95	$210.90
Purchase #5	$35.31	3.623%	$36.5893	$36.59	$36.60	$36.60
Purchase #6	$121.80	6.606%	$129.8461	$129.85	$129.85	$129.80
Purchase #7	$47.33	12.617%	$53.3016	$53.30	$53.30	$53.30
7 purchase totals =	$725.91		$786.1093	$786.12	$786.15	$786.10