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	$171.97	4.206%	$179.2031	$179.20	$179.20	$179.20
Purchase #2	$66.54	8.577%	$72.2471	$72.25	$72.25	$72.20
Purchase #3	$58.90	3.492%	$60.9568	$60.96	$60.95	$61.00
Purchase #4	$144.56	6.742%	$154.3062	$154.31	$154.30	$154.30
Purchase #5	$146.88	13.298%	$166.4121	$166.41	$166.40	$166.40
Purchase #6	$163.78	6.712%	$174.7729	$174.77	$174.75	$174.80
Purchase #7	$249.64	11.535%	$278.436	$278.44	$278.45	$278.40
7 purchase totals =	$1,002.27		$1,086.3342	$1,086.34	$1,086.30	$1,086.30