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	$142.79	5.853%	$151.1475	$151.15	$151.15	$151.10
Purchase #2	$38.30	6.506%	$40.7918	$40.79	$40.80	$40.80
Purchase #3	$105.51	3.511%	$109.2145	$109.21	$109.20	$109.20
Purchase #4	$205.54	9.488%	$225.0416	$225.04	$225.05	$225.00
Purchase #5	$239.48	7.643%	$257.7835	$257.78	$257.80	$257.80
Purchase #6	$138.95	9.694%	$152.4198	$152.42	$152.40	$152.40
Purchase #7	$153.76	13.724%	$174.862	$174.86	$174.85	$174.90
7 purchase totals =	$1,024.33		$1,111.2607	$1,111.25	$1,111.25	$1,111.20