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	$109.43	12.653%	$123.2762	$123.28	$123.30	$123.30
Purchase #2	$194.69	3.193%	$200.9065	$200.91	$200.90	$200.90
Purchase #3	$61.25	3.525%	$63.4091	$63.41	$63.40	$63.40
Purchase #4	$249.30	9.332%	$272.5647	$272.56	$272.55	$272.60
Purchase #5	$113.31	11.674%	$126.5378	$126.54	$126.55	$126.50
Purchase #6	$123.50	4.721%	$129.3304	$129.33	$129.35	$129.30
Purchase #7	$224.40	7.786%	$241.8718	$241.87	$241.85	$241.90
7 purchase totals =	$1,075.88		$1,157.8965	$1,157.90	$1,157.90	$1,157.90