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	$84.77	13.443%	$96.1656	$96.17	$96.15	$96.20
Purchase #2	$170.65	10.710%	$188.9266	$188.93	$188.95	$188.90
Purchase #3	$85.93	4.243%	$89.576	$89.58	$89.60	$89.60
Purchase #4	$151.93	12.601%	$171.0747	$171.07	$171.05	$171.10
Purchase #5	$151.33	10.426%	$167.1077	$167.11	$167.10	$167.10
Purchase #6	$240.84	10.430%	$265.9596	$265.96	$265.95	$266.00
Purchase #7	$36.55	11.793%	$40.8603	$40.86	$40.85	$40.90
7 purchase totals =	$922.00		$1,019.6705	$1,019.68	$1,019.65	$1,019.80