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	$236.36	7.797%	$254.789	$254.79	$254.80	$254.80
Purchase #2	$37.65	12.270%	$42.2697	$42.27	$42.25	$42.30
Purchase #3	$168.87	6.358%	$179.6068	$179.61	$179.60	$179.60
Purchase #4	$179.32	6.462%	$190.9077	$190.91	$190.90	$190.90
Purchase #5	$123.35	6.464%	$131.3233	$131.32	$131.30	$131.30
Purchase #6	$223.40	3.648%	$231.5496	$231.55	$231.55	$231.50
Purchase #7	$208.49	3.477%	$215.7392	$215.74	$215.75	$215.70
7 purchase totals =	$1,177.44		$1,246.1853	$1,246.19	$1,246.15	$1,246.10