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	$162.54	10.699%	$179.9302	$179.93	$179.95	$179.90
Purchase #2	$139.48	6.547%	$148.6118	$148.61	$148.60	$148.60
Purchase #3	$110.67	3.591%	$114.6442	$114.64	$114.65	$114.60
Purchase #4	$200.34	5.686%	$211.7313	$211.73	$211.75	$211.70
Purchase #5	$154.38	6.307%	$164.1167	$164.12	$164.10	$164.10
Purchase #6	$73.60	9.623%	$80.6825	$80.68	$80.70	$80.70
Purchase #7	$96.41	4.310%	$100.5653	$100.57	$100.55	$100.60
7 purchase totals =	$937.42		$1,000.2820	$1,000.28	$1,000.30	$1,000.20