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	$170.26	9.229%	$185.9733	$185.97	$185.95	$186.00
Purchase #2	$89.78	13.718%	$102.096	$102.10	$102.10	$102.10
Purchase #3	$148.96	11.819%	$166.5656	$166.57	$166.55	$166.60
Purchase #4	$60.55	11.583%	$67.5635	$67.56	$67.55	$67.60
Purchase #5	$224.95	12.292%	$252.6009	$252.60	$252.60	$252.60
Purchase #6	$129.98	12.780%	$146.5914	$146.59	$146.60	$146.60
Purchase #7	$91.82	5.563%	$96.9279	$96.93	$96.95	$96.90
7 purchase totals =	$916.30		$1,018.3186	$1,018.32	$1,018.30	$1,018.40