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	$150.32	9.373%	$164.4095	$164.41	$164.40	$164.40
Purchase #2	$142.26	5.720%	$150.3973	$150.40	$150.40	$150.40
Purchase #3	$115.63	9.251%	$126.3269	$126.33	$126.35	$126.30
Purchase #4	$201.51	8.461%	$218.5598	$218.56	$218.55	$218.60
Purchase #5	$145.89	4.197%	$152.013	$152.01	$152.00	$152.00
Purchase #6	$165.65	10.237%	$182.6076	$182.61	$182.60	$182.60
Purchase #7	$223.96	9.763%	$245.8252	$245.83	$245.85	$245.80
7 purchase totals =	$1,145.22		$1,240.1393	$1,240.15	$1,240.15	$1,240.10