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	$82.28	6.107%	$87.3048	$87.30	$87.30	$87.30
Purchase #2	$166.51	4.255%	$173.595	$173.60	$173.60	$173.60
Purchase #3	$92.50	7.616%	$99.5448	$99.54	$99.55	$99.50
Purchase #4	$141.28	7.591%	$152.0046	$152.00	$152.00	$152.00
Purchase #5	$25.70	10.651%	$28.4373	$28.44	$28.45	$28.40
Purchase #6	$77.71	6.264%	$82.5778	$82.58	$82.60	$82.60
Purchase #7	$202.60	9.508%	$221.8632	$221.86	$221.85	$221.90
7 purchase totals =	$788.58		$845.3275	$845.32	$845.35	$845.30