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	$42.26	5.389%	$44.5374	$44.54	$44.55	$44.50
Purchase #2	$118.95	6.800%	$127.0386	$127.04	$127.05	$127.00
Purchase #3	$109.85	4.514%	$114.8086	$114.81	$114.80	$114.80
Purchase #4	$41.90	11.122%	$46.5601	$46.56	$46.55	$46.60
Purchase #5	$43.65	6.274%	$46.3886	$46.39	$46.40	$46.40
Purchase #6	$246.43	3.144%	$254.1778	$254.18	$254.20	$254.20
Purchase #7	$242.34	4.614%	$253.5216	$253.52	$253.50	$253.50
7 purchase totals =	$845.38		$887.0327	$887.04	$887.05	$887.00