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	$225.59	5.663%	$238.3652	$238.37	$238.35	$238.40
Purchase #2	$148.83	5.219%	$156.5974	$156.60	$156.60	$156.60
Purchase #3	$233.31	4.449%	$243.69	$243.69	$243.70	$243.70
Purchase #4	$58.94	9.478%	$64.5263	$64.53	$64.55	$64.50
Purchase #5	$15.77	4.682%	$16.5084	$16.51	$16.50	$16.50
Purchase #6	$118.40	13.774%	$134.7084	$134.71	$134.70	$134.70
Purchase #7	$228.80	12.559%	$257.535	$257.54	$257.55	$257.50
7 purchase totals =	$1,029.64		$1,111.9307	$1,111.95	$1,111.95	$1,111.90