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	$224.44	8.726%	$244.0246	$244.02	$244.00	$244.00
Purchase #2	$225.59	10.596%	$249.4935	$249.49	$249.50	$249.50
Purchase #3	$31.25	8.265%	$33.8328	$33.83	$33.85	$33.80
Purchase #4	$127.36	12.167%	$142.8559	$142.86	$142.85	$142.90
Purchase #5	$151.98	11.476%	$169.4212	$169.42	$169.40	$169.40
Purchase #6	$59.95	8.204%	$64.8683	$64.87	$64.85	$64.90
Purchase #7	$151.32	3.310%	$156.3287	$156.33	$156.35	$156.30
7 purchase totals =	$971.89		$1,060.8250	$1,060.82	$1,060.80	$1,060.80