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	$173.53	13.103%	$196.2676	$196.27	$196.25	$196.30
Purchase #2	$62.56	12.356%	$70.2899	$70.29	$70.30	$70.30
Purchase #3	$116.79	3.508%	$120.887	$120.89	$120.90	$120.90
Purchase #4	$217.54	12.614%	$244.9805	$244.98	$245.00	$245.00
Purchase #5	$126.97	9.183%	$138.6297	$138.63	$138.65	$138.60
Purchase #6	$41.50	6.561%	$44.2228	$44.22	$44.20	$44.20
Purchase #7	$77.40	9.872%	$85.0409	$85.04	$85.05	$85.00
7 purchase totals =	$816.29		$900.3184	$900.32	$900.35	$900.30