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	$231.34	10.447%	$255.5081	$255.51	$255.50	$255.50
Purchase #2	$162.40	12.171%	$182.1657	$182.17	$182.15	$182.20
Purchase #3	$56.93	9.712%	$62.459	$62.46	$62.45	$62.50
Purchase #4	$21.96	3.787%	$22.7916	$22.79	$22.80	$22.80
Purchase #5	$185.74	4.801%	$194.6574	$194.66	$194.65	$194.70
Purchase #6	$116.25	9.607%	$127.4181	$127.42	$127.40	$127.40
Purchase #7	$49.62	12.707%	$55.9252	$55.93	$55.95	$55.90
7 purchase totals =	$824.24		$900.9251	$900.94	$900.90	$901.00