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	$151.97	8.133%	$164.3297	$164.33	$164.35	$164.30
Purchase #2	$109.69	11.177%	$121.9501	$121.95	$121.95	$122.00
Purchase #3	$217.31	6.684%	$231.835	$231.84	$231.85	$231.80
Purchase #4	$162.66	5.507%	$171.6177	$171.62	$171.60	$171.60
Purchase #5	$91.51	10.276%	$100.9136	$100.91	$100.90	$100.90
Purchase #6	$125.52	4.722%	$131.4471	$131.45	$131.45	$131.40
Purchase #7	$211.86	4.584%	$221.5717	$221.57	$221.55	$221.60
7 purchase totals =	$1,070.52		$1,143.6649	$1,143.67	$1,143.65	$1,143.60