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	$115.29	8.214%	$124.7599	$124.76	$124.75	$124.80
Purchase #2	$191.37	12.862%	$215.984	$215.98	$216.00	$216.00
Purchase #3	$142.85	4.768%	$149.6611	$149.66	$149.65	$149.70
Purchase #4	$175.78	11.873%	$196.6504	$196.65	$196.65	$196.70
Purchase #5	$40.26	4.368%	$42.0186	$42.02	$42.00	$42.00
Purchase #6	$217.36	11.589%	$242.5499	$242.55	$242.55	$242.50
Purchase #7	$57.95	3.161%	$59.7818	$59.78	$59.80	$59.80
7 purchase totals =	$940.86		$1,031.4057	$1,031.40	$1,031.40	$1,031.50