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	$143.42	13.126%	$162.2453	$162.25	$162.25	$162.20
Purchase #2	$106.76	7.675%	$114.9538	$114.95	$114.95	$115.00
Purchase #3	$241.53	6.335%	$256.8309	$256.83	$256.85	$256.80
Purchase #4	$247.33	6.399%	$263.1566	$263.16	$263.15	$263.20
Purchase #5	$222.75	6.860%	$238.0307	$238.03	$238.05	$238.00
Purchase #6	$68.55	4.606%	$71.7074	$71.71	$71.70	$71.70
Purchase #7	$21.27	13.522%	$24.1461	$24.15	$24.15	$24.10
7 purchase totals =	$1,051.61		$1,131.0708	$1,131.08	$1,131.10	$1,131.00