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	$79.29	8.458%	$85.9963	$86.00	$86.00	$86.00
Purchase #2	$15.78	7.779%	$17.0075	$17.01	$17.00	$17.00
Purchase #3	$152.63	9.736%	$167.4901	$167.49	$167.50	$167.50
Purchase #4	$25.54	7.369%	$27.422	$27.42	$27.40	$27.40
Purchase #5	$103.42	5.526%	$109.135	$109.14	$109.15	$109.10
Purchase #6	$86.61	4.299%	$90.3334	$90.33	$90.35	$90.30
Purchase #7	$206.41	13.126%	$233.5034	$233.50	$233.50	$233.50
7 purchase totals =	$669.68		$730.8877	$730.89	$730.90	$730.80