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	$103.46	10.206%	$114.0191	$114.02	$114.00	$114.00
Purchase #2	$121.30	8.304%	$131.3728	$131.37	$131.35	$131.40
Purchase #3	$51.40	3.400%	$53.1476	$53.15	$53.15	$53.10
Purchase #4	$217.45	7.392%	$233.5239	$233.52	$233.50	$233.50
Purchase #5	$135.72	7.449%	$145.8298	$145.83	$145.85	$145.80
Purchase #6	$149.50	10.788%	$165.6281	$165.63	$165.65	$165.60
Purchase #7	$35.29	6.315%	$37.5186	$37.52	$37.50	$37.50
7 purchase totals =	$814.12		$881.0399	$881.04	$881.00	$880.90