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	$48.90	9.309%	$53.4521	$53.45	$53.45	$53.50
Purchase #2	$146.38	6.800%	$156.3338	$156.33	$156.35	$156.30
Purchase #3	$14.46	5.236%	$15.2171	$15.22	$15.20	$15.20
Purchase #4	$87.69	7.218%	$94.0195	$94.02	$94.00	$94.00
Purchase #5	$22.65	12.373%	$25.4525	$25.45	$25.45	$25.50
Purchase #6	$178.79	3.819%	$185.618	$185.62	$185.60	$185.60
Purchase #7	$95.58	4.218%	$99.6116	$99.61	$99.60	$99.60
7 purchase totals =	$594.45		$629.7046	$629.70	$629.65	$629.70