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	$231.56	4.249%	$241.399	$241.40	$241.40	$241.40
Purchase #2	$181.28	12.759%	$204.4095	$204.41	$204.40	$204.40
Purchase #3	$77.59	7.343%	$83.2874	$83.29	$83.30	$83.30
Purchase #4	$38.55	13.181%	$43.6313	$43.63	$43.65	$43.60
Purchase #5	$182.52	9.784%	$200.3778	$200.38	$200.40	$200.40
Purchase #6	$94.87	9.816%	$104.1824	$104.18	$104.20	$104.20
Purchase #7	$166.59	12.510%	$187.4304	$187.43	$187.45	$187.40
7 purchase totals =	$972.96		$1,064.7178	$1,064.72	$1,064.80	$1,064.70