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	$54.75	11.687%	$61.1486	$61.15	$61.15	$61.10
Purchase #2	$101.33	12.289%	$113.7824	$113.78	$113.80	$113.80
Purchase #3	$18.25	7.868%	$19.6859	$19.69	$19.70	$19.70
Purchase #4	$162.27	3.769%	$168.386	$168.39	$168.40	$168.40
Purchase #5	$151.36	4.541%	$158.2333	$158.23	$158.25	$158.20
Purchase #6	$193.40	10.319%	$213.3569	$213.36	$213.35	$213.40
Purchase #7	$104.30	11.786%	$116.5928	$116.59	$116.60	$116.60
7 purchase totals =	$785.66		$851.1859	$851.19	$851.25	$851.20