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	$128.41	13.128%	$145.2677	$145.27	$145.25	$145.30
Purchase #2	$166.56	3.686%	$172.6994	$172.70	$172.70	$172.70
Purchase #3	$236.95	6.767%	$252.9844	$252.98	$253.00	$253.00
Purchase #4	$148.93	5.474%	$157.0824	$157.08	$157.10	$157.10
Purchase #5	$127.86	3.128%	$131.8595	$131.86	$131.85	$131.90
Purchase #6	$148.98	13.587%	$169.2219	$169.22	$169.20	$169.20
Purchase #7	$73.96	11.169%	$82.2206	$82.22	$82.20	$82.20
7 purchase totals =	$1,031.65		$1,111.3359	$1,111.33	$1,111.30	$1,111.40