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	$161.86	11.240%	$180.0531	$180.05	$180.05	$180.10
Purchase #2	$219.73	13.159%	$248.6443	$248.64	$248.65	$248.60
Purchase #3	$168.59	9.689%	$184.9247	$184.92	$184.90	$184.90
Purchase #4	$157.77	6.105%	$167.4019	$167.40	$167.40	$167.40
Purchase #5	$127.53	13.200%	$144.364	$144.36	$144.35	$144.40
Purchase #6	$17.49	11.217%	$19.4519	$19.45	$19.45	$19.50
Purchase #7	$84.50	6.167%	$89.7111	$89.71	$89.70	$89.70
7 purchase totals =	$937.47		$1,034.5510	$1,034.53	$1,034.50	$1,034.60