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	$82.52	6.758%	$88.0967	$88.10	$88.10	$88.10
Purchase #2	$91.97	3.451%	$95.1439	$95.14	$95.15	$95.10
Purchase #3	$74.71	5.202%	$78.5964	$78.60	$78.60	$78.60
Purchase #4	$233.79	11.702%	$261.1481	$261.15	$261.15	$261.10
Purchase #5	$220.71	10.711%	$244.3502	$244.35	$244.35	$244.40
Purchase #6	$211.27	6.318%	$224.618	$224.62	$224.60	$224.60
Purchase #7	$138.89	7.710%	$149.5984	$149.60	$149.60	$149.60
7 purchase totals =	$1,053.86		$1,141.5517	$1,141.56	$1,141.55	$1,141.50