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	$144.29	5.727%	$152.5535	$152.55	$152.55	$152.60
Purchase #2	$167.99	4.221%	$175.0809	$175.08	$175.10	$175.10
Purchase #3	$196.32	13.642%	$223.102	$223.10	$223.10	$223.10
Purchase #4	$150.43	12.237%	$168.8381	$168.84	$168.85	$168.80
Purchase #5	$158.37	13.745%	$180.138	$180.14	$180.15	$180.10
Purchase #6	$24.89	12.543%	$28.012	$28.01	$28.00	$28.00
Purchase #7	$239.75	5.597%	$253.1688	$253.17	$253.15	$253.20
7 purchase totals =	$1,082.04		$1,180.8933	$1,180.89	$1,180.90	$1,180.90