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	$174.36	6.244%	$185.247	$185.25	$185.25	$185.20
Purchase #2	$6.33	8.423%	$6.8632	$6.86	$6.85	$6.90
Purchase #3	$172.43	10.859%	$191.1542	$191.15	$191.15	$191.20
Purchase #4	$128.42	12.227%	$144.1219	$144.12	$144.10	$144.10
Purchase #5	$44.47	13.715%	$50.5691	$50.57	$50.55	$50.60
Purchase #6	$118.60	10.667%	$131.2511	$131.25	$131.25	$131.30
Purchase #7	$137.62	13.623%	$156.368	$156.37	$156.35	$156.40
7 purchase totals =	$782.23		$865.5745	$865.57	$865.50	$865.70