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	$221.48	3.115%	$228.3791	$228.38	$228.40	$228.40
Purchase #2	$40.25	13.512%	$45.6886	$45.69	$45.70	$45.70
Purchase #3	$200.49	13.673%	$227.903	$227.90	$227.90	$227.90
Purchase #4	$228.95	7.291%	$245.6427	$245.64	$245.65	$245.60
Purchase #5	$34.36	13.280%	$38.923	$38.92	$38.90	$38.90
Purchase #6	$87.70	4.363%	$91.5264	$91.53	$91.55	$91.50
Purchase #7	$154.42	6.727%	$164.8078	$164.81	$164.80	$164.80
7 purchase totals =	$967.65		$1,042.8706	$1,042.87	$1,042.90	$1,042.80