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	$117.52	8.717%	$127.7642	$127.76	$127.75	$127.80
Purchase #2	$93.47	5.438%	$98.5529	$98.55	$98.55	$98.60
Purchase #3	$85.63	4.143%	$89.1777	$89.18	$89.20	$89.20
Purchase #4	$11.42	12.524%	$12.8502	$12.85	$12.85	$12.90
Purchase #5	$52.52	13.369%	$59.5414	$59.54	$59.55	$59.50
Purchase #6	$193.60	8.586%	$210.2225	$210.22	$210.20	$210.20
Purchase #7	$231.98	13.469%	$263.2254	$263.23	$263.25	$263.20
7 purchase totals =	$786.14		$861.3343	$861.33	$861.35	$861.40