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	$214.52	6.129%	$227.6679	$227.67	$227.65	$227.70
Purchase #2	$188.58	11.270%	$209.833	$209.83	$209.85	$209.80
Purchase #3	$38.87	12.667%	$43.7937	$43.79	$43.80	$43.80
Purchase #4	$32.49	3.445%	$33.6093	$33.61	$33.60	$33.60
Purchase #5	$196.36	13.326%	$222.5269	$222.53	$222.55	$222.50
Purchase #6	$193.60	9.130%	$211.2757	$211.28	$211.30	$211.30
Purchase #7	$135.80	11.453%	$151.3532	$151.35	$151.35	$151.40
7 purchase totals =	$1,000.22		$1,100.0597	$1,100.06	$1,100.10	$1,100.10