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	$175.28	9.401%	$191.7581	$191.76	$191.75	$191.80
Purchase #2	$103.47	5.577%	$109.2405	$109.24	$109.25	$109.20
Purchase #3	$93.88	3.313%	$96.9902	$96.99	$97.00	$97.00
Purchase #4	$160.32	4.328%	$167.2586	$167.26	$167.25	$167.30
Purchase #5	$46.32	10.698%	$51.2753	$51.28	$51.30	$51.30
Purchase #6	$118.46	11.190%	$131.7157	$131.72	$131.70	$131.70
Purchase #7	$174.50	9.862%	$191.7092	$191.71	$191.70	$191.70
7 purchase totals =	$872.23		$939.9476	$939.96	$939.95	$940.00