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	$104.79	11.675%	$117.0242	$117.02	$117.00	$117.00
Purchase #2	$162.38	10.207%	$178.9541	$178.95	$178.95	$179.00
Purchase #3	$222.71	10.197%	$245.4197	$245.42	$245.40	$245.40
Purchase #4	$128.31	12.243%	$144.019	$144.02	$144.00	$144.00
Purchase #5	$134.77	10.779%	$149.2969	$149.30	$149.30	$149.30
Purchase #6	$78.76	10.318%	$86.8865	$86.89	$86.90	$86.90
Purchase #7	$68.78	4.172%	$71.6495	$71.65	$71.65	$71.60
7 purchase totals =	$900.50		$993.2499	$993.25	$993.20	$993.20