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	$237.92	11.269%	$264.7312	$264.73	$264.75	$264.70
Purchase #2	$23.54	10.503%	$26.0124	$26.01	$26.00	$26.00
Purchase #3	$135.79	4.786%	$142.2889	$142.29	$142.30	$142.30
Purchase #4	$182.42	7.605%	$196.293	$196.29	$196.30	$196.30
Purchase #5	$144.72	3.816%	$150.2425	$150.24	$150.25	$150.20
Purchase #6	$235.77	6.813%	$251.833	$251.83	$251.85	$251.80
Purchase #7	$49.57	11.342%	$55.1922	$55.19	$55.20	$55.20
7 purchase totals =	$1,009.73		$1,086.5932	$1,086.58	$1,086.65	$1,086.50