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	$78.93	8.764%	$85.8474	$85.85	$85.85	$85.80
Purchase #2	$80.82	6.386%	$85.9812	$85.98	$86.00	$86.00
Purchase #3	$186.37	6.532%	$198.5437	$198.54	$198.55	$198.50
Purchase #4	$174.89	10.700%	$193.6032	$193.60	$193.60	$193.60
Purchase #5	$145.88	10.362%	$160.9961	$161.00	$161.00	$161.00
Purchase #6	$51.97	4.609%	$54.3653	$54.37	$54.35	$54.40
Purchase #7	$187.45	3.521%	$194.0501	$194.05	$194.05	$194.10
7 purchase totals =	$906.31		$973.3870	$973.39	$973.40	$973.40