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	$233.88	4.588%	$244.6104	$244.61	$244.60	$244.60
Purchase #2	$120.83	5.797%	$127.8345	$127.83	$127.85	$127.80
Purchase #3	$90.85	3.465%	$93.998	$94.00	$94.00	$94.00
Purchase #4	$207.78	7.251%	$222.8461	$222.85	$222.85	$222.80
Purchase #5	$77.64	3.420%	$80.2953	$80.30	$80.30	$80.30
Purchase #6	$53.58	3.391%	$55.3969	$55.40	$55.40	$55.40
Purchase #7	$25.63	7.357%	$27.5156	$27.52	$27.50	$27.50
7 purchase totals =	$810.19		$852.4968	$852.51	$852.50	$852.40