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	$213.84	9.353%	$233.8405	$233.84	$233.85	$233.80
Purchase #2	$203.94	10.192%	$224.7256	$224.73	$224.75	$224.70
Purchase #3	$131.42	11.121%	$146.0352	$146.04	$146.05	$146.00
Purchase #4	$127.30	12.224%	$142.8612	$142.86	$142.85	$142.90
Purchase #5	$225.88	8.646%	$245.4096	$245.41	$245.40	$245.40
Purchase #6	$136.46	6.499%	$145.3285	$145.33	$145.35	$145.30
Purchase #7	$46.51	13.641%	$52.8544	$52.85	$52.85	$52.90
7 purchase totals =	$1,085.35		$1,191.0550	$1,191.06	$1,191.10	$1,191.00