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	$54.94	7.544%	$59.0847	$59.08	$59.10	$59.10
Purchase #2	$76.62	8.608%	$83.2154	$83.22	$83.20	$83.20
Purchase #3	$26.35	12.626%	$29.677	$29.68	$29.70	$29.70
Purchase #4	$150.89	7.752%	$162.587	$162.59	$162.60	$162.60
Purchase #5	$145.78	4.151%	$151.8313	$151.83	$151.85	$151.80
Purchase #6	$17.42	6.608%	$18.5711	$18.57	$18.55	$18.60
Purchase #7	$221.57	12.292%	$248.8054	$248.81	$248.80	$248.80
7 purchase totals =	$693.57		$753.7719	$753.78	$753.80	$753.80