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	$152.35	10.219%	$167.9186	$167.92	$167.90	$167.90
Purchase #2	$247.69	10.296%	$273.1922	$273.19	$273.20	$273.20
Purchase #3	$216.76	8.872%	$235.9909	$235.99	$236.00	$236.00
Purchase #4	$100.57	8.775%	$109.395	$109.40	$109.40	$109.40
Purchase #5	$139.65	13.660%	$158.7262	$158.73	$158.75	$158.70
Purchase #6	$28.72	8.220%	$31.0808	$31.08	$31.10	$31.10
Purchase #7	$199.82	10.159%	$220.1197	$220.12	$220.10	$220.10
7 purchase totals =	$1,085.56		$1,196.4234	$1,196.43	$1,196.45	$1,196.40