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	$146.61	12.171%	$164.4539	$164.45	$164.45	$164.50
Purchase #2	$139.50	5.458%	$147.1139	$147.11	$147.10	$147.10
Purchase #3	$95.87	11.508%	$106.9027	$106.90	$106.90	$106.90
Purchase #4	$82.65	11.157%	$91.8713	$91.87	$91.85	$91.90
Purchase #5	$202.65	9.776%	$222.4611	$222.46	$222.45	$222.50
Purchase #6	$106.39	4.175%	$110.8318	$110.83	$110.85	$110.80
Purchase #7	$233.48	8.386%	$253.0596	$253.06	$253.05	$253.10
7 purchase totals =	$1,007.15		$1,096.6943	$1,096.68	$1,096.65	$1,096.80