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	$196.90	10.142%	$216.8696	$216.87	$216.85	$216.90
Purchase #2	$70.65	3.181%	$72.8974	$72.90	$72.90	$72.90
Purchase #3	$103.82	3.735%	$107.6977	$107.70	$107.70	$107.70
Purchase #4	$243.50	12.494%	$273.9229	$273.92	$273.90	$273.90
Purchase #5	$110.61	12.305%	$124.2206	$124.22	$124.20	$124.20
Purchase #6	$151.47	8.314%	$164.0632	$164.06	$164.05	$164.10
Purchase #7	$160.72	12.340%	$180.5528	$180.55	$180.55	$180.60
7 purchase totals =	$1,037.67		$1,140.2242	$1,140.22	$1,140.15	$1,140.30