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	$249.33	3.241%	$257.4108	$257.41	$257.40	$257.40
Purchase #2	$169.44	9.366%	$185.3098	$185.31	$185.30	$185.30
Purchase #3	$100.69	5.598%	$106.3266	$106.33	$106.35	$106.30
Purchase #4	$31.66	3.767%	$32.8526	$32.85	$32.85	$32.90
Purchase #5	$64.67	11.304%	$71.9803	$71.98	$72.00	$72.00
Purchase #6	$245.68	4.276%	$256.1853	$256.19	$256.20	$256.20
Purchase #7	$221.33	9.113%	$241.4998	$241.50	$241.50	$241.50
7 purchase totals =	$1,082.80		$1,151.5652	$1,151.57	$1,151.60	$1,151.60