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	$142.78	6.520%	$152.0893	$152.09	$152.10	$152.10
Purchase #2	$164.95	12.183%	$185.0459	$185.05	$185.05	$185.00
Purchase #3	$243.33	3.364%	$251.5156	$251.52	$251.50	$251.50
Purchase #4	$59.44	10.423%	$65.6354	$65.64	$65.65	$65.60
Purchase #5	$122.81	9.129%	$134.0213	$134.02	$134.00	$134.00
Purchase #6	$59.55	5.486%	$62.8169	$62.82	$62.80	$62.80
Purchase #7	$231.68	7.802%	$249.7557	$249.76	$249.75	$249.80
7 purchase totals =	$1,024.54		$1,100.8801	$1,100.90	$1,100.85	$1,100.80