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	$129.52	10.142%	$142.6559	$142.66	$142.65	$142.70
Purchase #2	$195.44	7.760%	$210.6061	$210.61	$210.60	$210.60
Purchase #3	$134.89	3.629%	$139.7852	$139.79	$139.80	$139.80
Purchase #4	$27.45	4.408%	$28.66	$28.66	$28.65	$28.70
Purchase #5	$193.25	6.861%	$206.5089	$206.51	$206.50	$206.50
Purchase #6	$74.63	5.226%	$78.5302	$78.53	$78.55	$78.50
Purchase #7	$242.87	6.747%	$259.2564	$259.26	$259.25	$259.30
7 purchase totals =	$998.05		$1,066.0027	$1,066.02	$1,066.00	$1,066.10