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	$187.54	12.769%	$211.487	$211.49	$211.50	$211.50
Purchase #2	$70.59	5.683%	$74.6016	$74.60	$74.60	$74.60
Purchase #3	$69.26	4.518%	$72.3892	$72.39	$72.40	$72.40
Purchase #4	$72.32	10.310%	$79.7762	$79.78	$79.80	$79.80
Purchase #5	$155.68	6.674%	$166.0701	$166.07	$166.05	$166.10
Purchase #6	$55.65	6.628%	$59.3385	$59.34	$59.35	$59.30
Purchase #7	$105.47	11.430%	$117.5252	$117.53	$117.55	$117.50
7 purchase totals =	$716.51		$781.1878	$781.20	$781.25	$781.20