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	$168.90	7.337%	$181.2922	$181.29	$181.30	$181.30
Purchase #2	$61.51	6.331%	$65.4042	$65.40	$65.40	$65.40
Purchase #3	$150.37	5.871%	$159.1982	$159.20	$159.20	$159.20
Purchase #4	$178.39	6.705%	$190.351	$190.35	$190.35	$190.40
Purchase #5	$42.75	6.191%	$45.3967	$45.40	$45.40	$45.40
Purchase #6	$87.41	6.481%	$93.075	$93.08	$93.10	$93.10
Purchase #7	$85.45	3.586%	$88.5142	$88.51	$88.50	$88.50
7 purchase totals =	$774.78		$823.2315	$823.23	$823.25	$823.30