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	$168.98	8.828%	$183.8976	$183.90	$183.90	$183.90
Purchase #2	$60.73	3.253%	$62.7055	$62.71	$62.70	$62.70
Purchase #3	$45.36	9.146%	$49.5086	$49.51	$49.50	$49.50
Purchase #4	$159.28	10.241%	$175.5919	$175.59	$175.60	$175.60
Purchase #5	$88.84	5.716%	$93.9181	$93.92	$93.90	$93.90
Purchase #6	$107.36	3.697%	$111.3291	$111.33	$111.35	$111.30
Purchase #7	$142.96	5.336%	$150.5883	$150.59	$150.60	$150.60
7 purchase totals =	$773.51		$827.5391	$827.55	$827.55	$827.50