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	$148.68	5.331%	$156.6061	$156.61	$156.60	$156.60
Purchase #2	$223.76	3.366%	$231.2918	$231.29	$231.30	$231.30
Purchase #3	$37.73	7.586%	$40.5922	$40.59	$40.60	$40.60
Purchase #4	$86.28	5.691%	$91.1902	$91.19	$91.20	$91.20
Purchase #5	$229.82	10.758%	$254.544	$254.54	$254.55	$254.50
Purchase #6	$143.89	9.531%	$157.6042	$157.60	$157.60	$157.60
Purchase #7	$238.71	12.109%	$267.6154	$267.62	$267.60	$267.60
7 purchase totals =	$1,108.87		$1,199.4439	$1,199.44	$1,199.45	$1,199.40