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	$202.96	11.393%	$226.0832	$226.08	$226.10	$226.10
Purchase #2	$61.72	6.740%	$65.8799	$65.88	$65.90	$65.90
Purchase #3	$208.25	7.789%	$224.4706	$224.47	$224.45	$224.50
Purchase #4	$75.83	6.126%	$80.4753	$80.48	$80.50	$80.50
Purchase #5	$121.25	5.708%	$128.171	$128.17	$128.15	$128.20
Purchase #6	$103.82	3.679%	$107.6395	$107.64	$107.65	$107.60
Purchase #7	$175.64	6.511%	$187.0759	$187.08	$187.10	$187.10
7 purchase totals =	$949.47		$1,019.7954	$1,019.80	$1,019.85	$1,019.90