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	$162.40	4.398%	$169.5424	$169.54	$169.55	$169.50
Purchase #2	$112.46	13.602%	$127.7568	$127.76	$127.75	$127.80
Purchase #3	$103.92	6.641%	$110.8213	$110.82	$110.80	$110.80
Purchase #4	$177.68	8.262%	$192.3599	$192.36	$192.35	$192.40
Purchase #5	$99.43	9.752%	$109.1264	$109.13	$109.15	$109.10
Purchase #6	$245.26	12.667%	$276.3271	$276.33	$276.35	$276.30
Purchase #7	$126.97	3.617%	$131.5625	$131.56	$131.55	$131.60
7 purchase totals =	$1,028.12		$1,117.4964	$1,117.50	$1,117.50	$1,117.50