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	$189.96	6.644%	$202.5809	$202.58	$202.60	$202.60
Purchase #2	$89.45	5.550%	$94.4145	$94.41	$94.40	$94.40
Purchase #3	$191.86	10.771%	$212.5252	$212.53	$212.55	$212.50
Purchase #4	$95.37	4.106%	$99.2859	$99.29	$99.30	$99.30
Purchase #5	$164.76	10.816%	$182.5804	$182.58	$182.60	$182.60
Purchase #6	$219.51	13.848%	$249.9077	$249.91	$249.90	$249.90
Purchase #7	$73.48	6.549%	$78.2922	$78.29	$78.30	$78.30
7 purchase totals =	$1,024.39		$1,119.5868	$1,119.59	$1,119.65	$1,119.60