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	$67.42	7.651%	$72.5783	$72.58	$72.60	$72.60
Purchase #2	$242.88	7.312%	$260.6394	$260.64	$260.65	$260.60
Purchase #3	$162.47	3.137%	$167.5667	$167.57	$167.55	$167.60
Purchase #4	$179.89	6.271%	$191.1709	$191.17	$191.15	$191.20
Purchase #5	$208.93	11.714%	$233.4041	$233.40	$233.40	$233.40
Purchase #6	$154.90	8.826%	$168.5715	$168.57	$168.55	$168.60
Purchase #7	$145.62	12.623%	$164.0016	$164.00	$164.00	$164.00
7 purchase totals =	$1,162.11		$1,257.9325	$1,257.93	$1,257.90	$1,258.00