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	$52.84	12.601%	$59.4984	$59.50	$59.50	$59.50
Purchase #2	$130.76	10.127%	$144.0021	$144.00	$144.00	$144.00
Purchase #3	$203.39	9.840%	$223.4036	$223.40	$223.40	$223.40
Purchase #4	$167.38	12.244%	$187.874	$187.87	$187.85	$187.90
Purchase #5	$52.56	11.800%	$58.7621	$58.76	$58.75	$58.80
Purchase #6	$191.57	10.424%	$211.5393	$211.54	$211.55	$211.50
Purchase #7	$17.87	9.620%	$19.5891	$19.59	$19.60	$19.60
7 purchase totals =	$816.37		$904.6686	$904.66	$904.65	$904.70