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	$114.67	11.312%	$127.6415	$127.64	$127.65	$127.60
Purchase #2	$207.63	8.763%	$225.8246	$225.82	$225.80	$225.80
Purchase #3	$74.38	10.474%	$82.1706	$82.17	$82.15	$82.20
Purchase #4	$129.53	5.203%	$136.2694	$136.27	$136.25	$136.30
Purchase #5	$118.31	13.615%	$134.4179	$134.42	$134.40	$134.40
Purchase #6	$225.77	11.122%	$250.8801	$250.88	$250.90	$250.90
Purchase #7	$138.61	11.650%	$154.7581	$154.76	$154.75	$154.80
7 purchase totals =	$1,008.90		$1,111.9622	$1,111.96	$1,111.90	$1,112.00