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	$117.34	5.313%	$123.5743	$123.57	$123.55	$123.60
Purchase #2	$95.93	8.138%	$103.7368	$103.74	$103.75	$103.70
Purchase #3	$174.36	3.373%	$180.2412	$180.24	$180.25	$180.20
Purchase #4	$152.75	8.661%	$165.9797	$165.98	$166.00	$166.00
Purchase #5	$135.98	10.699%	$150.5285	$150.53	$150.55	$150.50
Purchase #6	$96.46	3.444%	$99.7821	$99.78	$99.80	$99.80
Purchase #7	$107.61	5.482%	$113.5092	$113.51	$113.50	$113.50
7 purchase totals =	$880.43		$937.3518	$937.35	$937.40	$937.30