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	$105.80	13.586%	$120.174	$120.17	$120.15	$120.20
Purchase #2	$140.72	11.495%	$156.8958	$156.90	$156.90	$156.90
Purchase #3	$147.81	11.522%	$164.8407	$164.84	$164.85	$164.80
Purchase #4	$158.60	7.454%	$170.422	$170.42	$170.40	$170.40
Purchase #5	$190.76	7.752%	$205.5477	$205.55	$205.55	$205.50
Purchase #6	$135.57	4.421%	$141.5635	$141.56	$141.55	$141.60
Purchase #7	$200.92	6.138%	$213.2525	$213.25	$213.25	$213.30
7 purchase totals =	$1,080.18		$1,172.6962	$1,172.69	$1,172.65	$1,172.70