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	$81.39	13.640%	$92.4916	$92.49	$92.50	$92.50
Purchase #2	$138.75	6.540%	$147.8243	$147.82	$147.80	$147.80
Purchase #3	$124.72	6.263%	$132.5312	$132.53	$132.55	$132.50
Purchase #4	$144.36	5.611%	$152.46	$152.46	$152.45	$152.50
Purchase #5	$214.82	13.820%	$244.5081	$244.51	$244.50	$244.50
Purchase #6	$64.45	13.861%	$73.3834	$73.38	$73.40	$73.40
Purchase #7	$179.68	3.421%	$185.8269	$185.83	$185.85	$185.80
7 purchase totals =	$948.17		$1,029.0255	$1,029.02	$1,029.05	$1,029.00