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	$62.69	7.489%	$67.3849	$67.38	$67.40	$67.40
Purchase #2	$75.78	10.506%	$83.7414	$83.74	$83.75	$83.70
Purchase #3	$201.59	12.790%	$227.3734	$227.37	$227.35	$227.40
Purchase #4	$94.68	4.710%	$99.1394	$99.14	$99.15	$99.10
Purchase #5	$35.51	9.598%	$38.9182	$38.92	$38.90	$38.90
Purchase #6	$234.54	4.447%	$244.97	$244.97	$244.95	$245.00
Purchase #7	$27.32	4.126%	$28.4472	$28.45	$28.45	$28.40
7 purchase totals =	$732.11		$789.9745	$789.97	$789.95	$789.90