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	$240.26	9.808%	$263.8247	$263.82	$263.80	$263.80
Purchase #2	$17.86	8.362%	$19.3535	$19.35	$19.35	$19.40
Purchase #3	$89.27	13.691%	$101.492	$101.49	$101.50	$101.50
Purchase #4	$94.81	6.340%	$100.821	$100.82	$100.80	$100.80
Purchase #5	$248.92	3.176%	$256.8257	$256.83	$256.85	$256.80
Purchase #6	$189.77	8.384%	$205.6803	$205.68	$205.70	$205.70
Purchase #7	$211.42	10.358%	$233.3189	$233.32	$233.30	$233.30
7 purchase totals =	$1,092.31		$1,181.3161	$1,181.31	$1,181.30	$1,181.30