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	$23.95	9.749%	$26.2849	$26.28	$26.30	$26.30
Purchase #2	$168.79	9.213%	$184.3406	$184.34	$184.35	$184.30
Purchase #3	$30.31	6.472%	$32.2717	$32.27	$32.25	$32.30
Purchase #4	$97.86	13.869%	$111.4322	$111.43	$111.45	$111.40
Purchase #5	$228.56	4.135%	$238.011	$238.01	$238.00	$238.00
Purchase #6	$234.89	6.687%	$250.5971	$250.60	$250.60	$250.60
Purchase #7	$194.39	3.274%	$200.7543	$200.75	$200.75	$200.80
7 purchase totals =	$978.75		$1,043.6918	$1,043.68	$1,043.70	$1,043.70