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	$109.32	8.226%	$118.3127	$118.31	$118.30	$118.30
Purchase #2	$27.67	13.806%	$31.4901	$31.49	$31.50	$31.50
Purchase #3	$106.99	12.413%	$120.2707	$120.27	$120.25	$120.30
Purchase #4	$90.90	12.265%	$102.0489	$102.05	$102.05	$102.00
Purchase #5	$39.61	5.581%	$41.8206	$41.82	$41.80	$41.80
Purchase #6	$149.82	9.670%	$164.3076	$164.31	$164.30	$164.30
Purchase #7	$150.98	7.569%	$162.4077	$162.41	$162.40	$162.40
7 purchase totals =	$675.29		$740.6583	$740.66	$740.60	$740.60