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	$69.82	4.257%	$72.7922	$72.79	$72.80	$72.80
Purchase #2	$52.72	9.570%	$57.7653	$57.77	$57.75	$57.80
Purchase #3	$249.56	4.293%	$260.2736	$260.27	$260.25	$260.30
Purchase #4	$80.87	9.299%	$88.3901	$88.39	$88.40	$88.40
Purchase #5	$88.86	12.596%	$100.0528	$100.05	$100.05	$100.10
Purchase #6	$59.76	12.202%	$67.0519	$67.05	$67.05	$67.10
Purchase #7	$246.36	9.778%	$270.4491	$270.45	$270.45	$270.40
7 purchase totals =	$847.95		$916.7750	$916.77	$916.75	$916.90