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	$93.60	10.677%	$103.5937	$103.59	$103.60	$103.60
Purchase #2	$244.84	9.300%	$267.6101	$267.61	$267.60	$267.60
Purchase #3	$244.29	9.278%	$266.9552	$266.96	$266.95	$267.00
Purchase #4	$111.37	3.189%	$114.9216	$114.92	$114.90	$114.90
Purchase #5	$38.43	12.753%	$43.331	$43.33	$43.35	$43.30
Purchase #6	$91.78	7.138%	$98.3313	$98.33	$98.35	$98.30
Purchase #7	$95.57	11.680%	$106.7326	$106.73	$106.75	$106.70
7 purchase totals =	$919.88		$1,001.4755	$1,001.47	$1,001.50	$1,001.40