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	$144.54	9.519%	$158.2988	$158.30	$158.30	$158.30
Purchase #2	$184.82	11.750%	$206.5364	$206.54	$206.55	$206.50
Purchase #3	$112.69	13.184%	$127.547	$127.55	$127.55	$127.50
Purchase #4	$23.79	6.771%	$25.4008	$25.40	$25.40	$25.40
Purchase #5	$179.50	9.616%	$196.7607	$196.76	$196.75	$196.80
Purchase #6	$247.79	7.685%	$266.8327	$266.83	$266.85	$266.80
Purchase #7	$57.82	6.804%	$61.7541	$61.75	$61.75	$61.80
7 purchase totals =	$950.95		$1,043.1305	$1,043.13	$1,043.15	$1,043.10