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	$146.42	10.372%	$161.6067	$161.61	$161.60	$161.60
Purchase #2	$74.93	10.123%	$82.5152	$82.52	$82.50	$82.50
Purchase #3	$237.86	12.272%	$267.0502	$267.05	$267.05	$267.10
Purchase #4	$35.80	4.572%	$37.4368	$37.44	$37.45	$37.40
Purchase #5	$217.84	12.578%	$245.2399	$245.24	$245.25	$245.20
Purchase #6	$149.49	9.384%	$163.5181	$163.52	$163.50	$163.50
Purchase #7	$179.94	11.300%	$200.2732	$200.27	$200.25	$200.30
7 purchase totals =	$1,042.28		$1,157.6401	$1,157.65	$1,157.60	$1,157.60