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	$151.26	8.668%	$164.3712	$164.37	$164.35	$164.40
Purchase #2	$163.76	5.166%	$172.2198	$172.22	$172.20	$172.20
Purchase #3	$162.82	11.651%	$181.7902	$181.79	$181.80	$181.80
Purchase #4	$191.37	8.513%	$207.6613	$207.66	$207.65	$207.70
Purchase #5	$206.91	8.715%	$224.9422	$224.94	$224.95	$224.90
Purchase #6	$75.56	3.168%	$77.9537	$77.95	$77.95	$78.00
Purchase #7	$160.28	4.749%	$167.8917	$167.89	$167.90	$167.90
7 purchase totals =	$1,111.96		$1,196.8301	$1,196.82	$1,196.80	$1,196.90