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	$140.31	10.223%	$154.6539	$154.65	$154.65	$154.70
Purchase #2	$38.77	3.128%	$39.9827	$39.98	$40.00	$40.00
Purchase #3	$80.78	11.241%	$89.8605	$89.86	$89.85	$89.90
Purchase #4	$248.41	7.561%	$267.1923	$267.19	$267.20	$267.20
Purchase #5	$216.97	7.739%	$233.7613	$233.76	$233.75	$233.80
Purchase #6	$184.70	3.504%	$191.1719	$191.17	$191.15	$191.20
Purchase #7	$97.74	13.874%	$111.3004	$111.30	$111.30	$111.30
7 purchase totals =	$1,007.68		$1,087.9230	$1,087.91	$1,087.90	$1,088.10