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	$137.79	10.147%	$151.7716	$151.77	$151.75	$151.80
Purchase #2	$121.52	11.348%	$135.3101	$135.31	$135.30	$135.30
Purchase #3	$91.42	13.671%	$103.918	$103.92	$103.90	$103.90
Purchase #4	$213.78	8.804%	$232.6012	$232.60	$232.60	$232.60
Purchase #5	$162.59	5.846%	$172.095	$172.10	$172.10	$172.10
Purchase #6	$106.96	10.221%	$117.8924	$117.89	$117.90	$117.90
Purchase #7	$79.93	11.483%	$89.1084	$89.11	$89.10	$89.10
7 purchase totals =	$913.99		$1,002.6967	$1,002.70	$1,002.65	$1,002.70