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	$105.64	4.556%	$110.453	$110.45	$110.45	$110.50
Purchase #2	$152.51	9.861%	$167.549	$167.55	$167.55	$167.50
Purchase #3	$37.93	6.113%	$40.2487	$40.25	$40.25	$40.20
Purchase #4	$178.47	4.335%	$186.2067	$186.21	$186.20	$186.20
Purchase #5	$54.55	9.477%	$59.7197	$59.72	$59.70	$59.70
Purchase #6	$5.53	12.183%	$6.2037	$6.20	$6.20	$6.20
Purchase #7	$226.88	10.378%	$250.4256	$250.43	$250.45	$250.40
7 purchase totals =	$761.51		$820.8064	$820.81	$820.80	$820.70