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	$201.32	9.759%	$220.9668	$220.97	$220.95	$221.00
Purchase #2	$96.71	3.674%	$100.2631	$100.26	$100.25	$100.30
Purchase #3	$196.47	13.528%	$223.0485	$223.05	$223.05	$223.00
Purchase #4	$92.46	9.385%	$101.1374	$101.14	$101.15	$101.10
Purchase #5	$120.59	5.244%	$126.9137	$126.91	$126.90	$126.90
Purchase #6	$171.33	4.234%	$178.5841	$178.58	$178.60	$178.60
Purchase #7	$104.73	11.643%	$116.9237	$116.92	$116.90	$116.90
7 purchase totals =	$983.61		$1,067.8373	$1,067.83	$1,067.80	$1,067.80