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	$154.98	4.793%	$162.4082	$162.41	$162.40	$162.40
Purchase #2	$99.80	10.720%	$110.4986	$110.50	$110.50	$110.50
Purchase #3	$224.34	13.830%	$255.3662	$255.37	$255.35	$255.40
Purchase #4	$137.48	10.484%	$151.8934	$151.89	$151.90	$151.90
Purchase #5	$104.78	13.585%	$119.0144	$119.01	$119.00	$119.00
Purchase #6	$225.29	6.718%	$240.425	$240.43	$240.45	$240.40
Purchase #7	$127.55	6.478%	$135.8127	$135.81	$135.80	$135.80
7 purchase totals =	$1,074.22		$1,175.4185	$1,175.42	$1,175.40	$1,175.40