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	$156.29	13.274%	$177.0359	$177.04	$177.05	$177.00
Purchase #2	$166.59	12.517%	$187.4421	$187.44	$187.45	$187.40
Purchase #3	$140.43	13.637%	$159.5804	$159.58	$159.60	$159.60
Purchase #4	$188.42	6.174%	$200.0531	$200.05	$200.05	$200.10
Purchase #5	$146.65	4.286%	$152.9354	$152.94	$152.95	$152.90
Purchase #6	$62.83	10.310%	$69.3078	$69.31	$69.30	$69.30
Purchase #7	$159.65	3.376%	$165.0398	$165.04	$165.05	$165.00
7 purchase totals =	$1,020.86		$1,111.3945	$1,111.40	$1,111.45	$1,111.30