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	$23.60	7.331%	$25.3301	$25.33	$25.35	$25.30
Purchase #2	$50.57	10.433%	$55.846	$55.85	$55.85	$55.80
Purchase #3	$123.31	3.743%	$127.9255	$127.93	$127.95	$127.90
Purchase #4	$48.32	11.740%	$53.9928	$53.99	$54.00	$54.00
Purchase #5	$36.88	5.658%	$38.9667	$38.97	$38.95	$39.00
Purchase #6	$12.53	10.448%	$13.8391	$13.84	$13.85	$13.80
Purchase #7	$59.30	5.254%	$62.4156	$62.42	$62.40	$62.40
7 purchase totals =	$354.51		$378.3158	$378.33	$378.35	$378.20