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	$155.29	7.543%	$167.0035	$167.00	$167.00	$167.00
Purchase #2	$204.65	4.519%	$213.8981	$213.90	$213.90	$213.90
Purchase #3	$139.84	9.213%	$152.7235	$152.72	$152.70	$152.70
Purchase #4	$126.68	9.850%	$139.158	$139.16	$139.15	$139.20
Purchase #5	$139.34	7.661%	$150.0148	$150.01	$150.00	$150.00
Purchase #6	$149.85	10.687%	$165.8645	$165.86	$165.85	$165.90
Purchase #7	$135.71	12.387%	$152.5204	$152.52	$152.50	$152.50
7 purchase totals =	$1,051.36		$1,141.1828	$1,141.17	$1,141.10	$1,141.20