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	$229.45	5.354%	$241.7348	$241.73	$241.75	$241.70
Purchase #2	$204.49	4.375%	$213.4364	$213.44	$213.45	$213.40
Purchase #3	$98.68	13.366%	$111.8696	$111.87	$111.85	$111.90
Purchase #4	$242.85	10.599%	$268.5897	$268.59	$268.60	$268.60
Purchase #5	$144.80	5.644%	$152.9725	$152.97	$152.95	$153.00
Purchase #6	$193.56	3.544%	$200.4198	$200.42	$200.40	$200.40
Purchase #7	$188.88	12.586%	$212.6524	$212.65	$212.65	$212.70
7 purchase totals =	$1,302.71		$1,401.6752	$1,401.67	$1,401.65	$1,401.70