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	$118.32	13.408%	$134.1843	$134.18	$134.20	$134.20
Purchase #2	$57.56	13.441%	$65.2966	$65.30	$65.30	$65.30
Purchase #3	$108.84	4.789%	$114.0523	$114.05	$114.05	$114.10
Purchase #4	$112.51	3.340%	$116.2678	$116.27	$116.25	$116.30
Purchase #5	$211.82	13.521%	$240.4602	$240.46	$240.45	$240.50
Purchase #6	$211.76	6.294%	$225.0882	$225.09	$225.10	$225.10
Purchase #7	$68.73	4.577%	$71.8758	$71.88	$71.90	$71.90
7 purchase totals =	$889.54		$967.2252	$967.23	$967.25	$967.40