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	$12.36	4.137%	$12.8713	$12.87	$12.85	$12.90
Purchase #2	$150.66	7.511%	$161.9761	$161.98	$162.00	$162.00
Purchase #3	$138.47	3.374%	$143.142	$143.14	$143.15	$143.10
Purchase #4	$204.83	10.501%	$226.3392	$226.34	$226.35	$226.30
Purchase #5	$75.49	4.418%	$78.8251	$78.83	$78.85	$78.80
Purchase #6	$165.34	9.326%	$180.7596	$180.76	$180.75	$180.80
Purchase #7	$91.32	9.721%	$100.1972	$100.20	$100.20	$100.20
7 purchase totals =	$838.47		$904.1105	$904.12	$904.15	$904.10