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	$161.85	10.633%	$179.0595	$179.06	$179.05	$179.10
Purchase #2	$111.54	11.642%	$124.5255	$124.53	$124.55	$124.50
Purchase #3	$93.87	12.181%	$105.3043	$105.30	$105.30	$105.30
Purchase #4	$71.66	3.174%	$73.9345	$73.93	$73.95	$73.90
Purchase #5	$219.70	10.122%	$241.938	$241.94	$241.95	$241.90
Purchase #6	$91.44	8.692%	$99.388	$99.39	$99.40	$99.40
Purchase #7	$180.30	11.249%	$200.5819	$200.58	$200.60	$200.60
7 purchase totals =	$930.36		$1,024.7317	$1,024.73	$1,024.80	$1,024.70