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	$179.67	4.762%	$188.2259	$188.23	$188.25	$188.20
Purchase #2	$41.44	10.565%	$45.8181	$45.82	$45.80	$45.80
Purchase #3	$81.83	9.301%	$89.441	$89.44	$89.45	$89.40
Purchase #4	$61.92	10.798%	$68.6061	$68.61	$68.60	$68.60
Purchase #5	$227.51	7.536%	$244.6552	$244.66	$244.65	$244.70
Purchase #6	$214.73	9.689%	$235.5352	$235.54	$235.55	$235.50
Purchase #7	$214.66	10.652%	$237.5256	$237.53	$237.55	$237.50
7 purchase totals =	$1,021.76		$1,109.8071	$1,109.83	$1,109.85	$1,109.70