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	$167.36	3.698%	$173.549	$173.55	$173.55	$173.50
Purchase #2	$241.30	5.451%	$254.4533	$254.45	$254.45	$254.50
Purchase #3	$82.89	9.224%	$90.5358	$90.54	$90.55	$90.50
Purchase #4	$228.39	8.115%	$246.9238	$246.92	$246.90	$246.90
Purchase #5	$179.70	5.571%	$189.7111	$189.71	$189.70	$189.70
Purchase #6	$245.40	11.677%	$274.0554	$274.06	$274.05	$274.10
Purchase #7	$86.29	9.643%	$94.6109	$94.61	$94.60	$94.60
7 purchase totals =	$1,231.33		$1,323.8393	$1,323.84	$1,323.80	$1,323.80