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	$134.94	7.248%	$144.7205	$144.72	$144.70	$144.70
Purchase #2	$88.33	8.417%	$95.7647	$95.76	$95.75	$95.80
Purchase #3	$249.37	12.524%	$280.6011	$280.60	$280.60	$280.60
Purchase #4	$192.38	5.670%	$203.2879	$203.29	$203.30	$203.30
Purchase #5	$181.44	6.760%	$193.7053	$193.71	$193.70	$193.70
Purchase #6	$121.26	5.222%	$127.5922	$127.59	$127.60	$127.60
Purchase #7	$76.29	8.204%	$82.5488	$82.55	$82.55	$82.50
7 purchase totals =	$1,044.01		$1,128.2205	$1,128.22	$1,128.20	$1,128.20