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	$17.27	5.609%	$18.2387	$18.24	$18.25	$18.20
Purchase #2	$142.74	5.212%	$150.1796	$150.18	$150.20	$150.20
Purchase #3	$195.52	11.805%	$218.6011	$218.60	$218.60	$218.60
Purchase #4	$110.38	12.829%	$124.5407	$124.54	$124.55	$124.50
Purchase #5	$154.27	6.804%	$164.7665	$164.77	$164.75	$164.80
Purchase #6	$144.78	11.498%	$161.4268	$161.43	$161.45	$161.40
Purchase #7	$180.76	5.433%	$190.5807	$190.58	$190.60	$190.60
7 purchase totals =	$945.72		$1,028.3341	$1,028.34	$1,028.40	$1,028.30