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	$152.25	5.739%	$160.9876	$160.99	$161.00	$161.00
Purchase #2	$55.51	3.502%	$57.454	$57.45	$57.45	$57.50
Purchase #3	$29.61	5.742%	$31.3102	$31.31	$31.30	$31.30
Purchase #4	$152.25	10.362%	$168.0261	$168.03	$168.05	$168.00
Purchase #5	$116.38	8.492%	$126.263	$126.26	$126.25	$126.30
Purchase #6	$83.38	8.189%	$90.208	$90.21	$90.20	$90.20
Purchase #7	$67.39	9.276%	$73.6411	$73.64	$73.65	$73.60
7 purchase totals =	$656.77		$707.8900	$707.89	$707.90	$707.90