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	$171.43	4.208%	$178.6438	$178.64	$178.65	$178.60
Purchase #2	$51.71	10.248%	$57.0092	$57.01	$57.00	$57.00
Purchase #3	$200.99	10.722%	$222.5401	$222.54	$222.55	$222.50
Purchase #4	$241.44	4.326%	$251.8847	$251.88	$251.90	$251.90
Purchase #5	$130.33	4.214%	$135.8221	$135.82	$135.80	$135.80
Purchase #6	$131.45	7.360%	$141.1247	$141.12	$141.10	$141.10
Purchase #7	$52.30	4.825%	$54.8235	$54.82	$54.80	$54.80
7 purchase totals =	$979.65		$1,041.8481	$1,041.83	$1,041.80	$1,041.70