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	$71.96	13.675%	$81.8005	$81.80	$81.80	$81.80
Purchase #2	$201.32	3.673%	$208.7145	$208.71	$208.70	$208.70
Purchase #3	$239.59	6.658%	$255.5419	$255.54	$255.55	$255.50
Purchase #4	$44.41	8.602%	$48.2301	$48.23	$48.25	$48.20
Purchase #5	$223.90	4.190%	$233.2814	$233.28	$233.30	$233.30
Purchase #6	$82.63	8.223%	$89.4247	$89.42	$89.40	$89.40
Purchase #7	$148.26	5.654%	$156.6426	$156.64	$156.65	$156.60
7 purchase totals =	$1,012.07		$1,073.6357	$1,073.62	$1,073.65	$1,073.50