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	$164.67	13.820%	$187.4274	$187.43	$187.45	$187.40
Purchase #2	$63.56	10.591%	$70.2916	$70.29	$70.30	$70.30
Purchase #3	$227.56	7.402%	$244.404	$244.40	$244.40	$244.40
Purchase #4	$96.43	10.504%	$106.559	$106.56	$106.55	$106.60
Purchase #5	$176.84	13.431%	$200.5914	$200.59	$200.60	$200.60
Purchase #6	$149.64	10.554%	$165.433	$165.43	$165.45	$165.40
Purchase #7	$47.32	12.742%	$53.3495	$53.35	$53.35	$53.30
7 purchase totals =	$926.02		$1,028.0559	$1,028.05	$1,028.10	$1,028.00