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	$124.38	5.557%	$131.2918	$131.29	$131.30	$131.30
Purchase #2	$99.76	12.361%	$112.0913	$112.09	$112.10	$112.10
Purchase #3	$188.97	10.190%	$208.226	$208.23	$208.25	$208.20
Purchase #4	$233.56	8.592%	$253.6275	$253.63	$253.65	$253.60
Purchase #5	$9.77	10.250%	$10.7714	$10.77	$10.75	$10.80
Purchase #6	$64.50	6.686%	$68.8125	$68.81	$68.80	$68.80
Purchase #7	$207.40	12.420%	$233.1591	$233.16	$233.15	$233.20
7 purchase totals =	$928.34		$1,017.9796	$1,017.98	$1,018.00	$1,018.00