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	$132.51	13.230%	$150.0411	$150.04	$150.05	$150.00
Purchase #2	$96.46	5.205%	$101.4807	$101.48	$101.50	$101.50
Purchase #3	$178.57	10.495%	$197.3109	$197.31	$197.30	$197.30
Purchase #4	$146.69	9.192%	$160.1737	$160.17	$160.15	$160.20
Purchase #5	$155.25	9.803%	$170.4692	$170.47	$170.45	$170.50
Purchase #6	$165.86	9.435%	$181.5089	$181.51	$181.50	$181.50
Purchase #7	$89.40	10.645%	$98.9166	$98.92	$98.90	$98.90
7 purchase totals =	$964.74		$1,059.9011	$1,059.90	$1,059.85	$1,059.90