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	$93.43	9.815%	$102.6002	$102.60	$102.60	$102.60
Purchase #2	$104.74	9.714%	$114.9144	$114.91	$114.90	$114.90
Purchase #3	$159.92	4.773%	$167.553	$167.55	$167.55	$167.60
Purchase #4	$29.82	13.819%	$33.9408	$33.94	$33.95	$33.90
Purchase #5	$141.49	6.123%	$150.1534	$150.15	$150.15	$150.20
Purchase #6	$97.83	8.301%	$105.9509	$105.95	$105.95	$106.00
Purchase #7	$241.43	10.665%	$267.1785	$267.18	$267.20	$267.20
7 purchase totals =	$868.66		$942.2912	$942.28	$942.30	$942.40