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	$172.38	4.398%	$179.9613	$179.96	$179.95	$180.00
Purchase #2	$188.59	13.241%	$213.5612	$213.56	$213.55	$213.60
Purchase #3	$164.70	9.509%	$180.3613	$180.36	$180.35	$180.40
Purchase #4	$56.79	4.478%	$59.3331	$59.33	$59.35	$59.30
Purchase #5	$59.44	13.552%	$67.4953	$67.50	$67.50	$67.50
Purchase #6	$214.67	11.686%	$239.7563	$239.76	$239.75	$239.80
Purchase #7	$175.99	3.817%	$182.7075	$182.71	$182.70	$182.70
7 purchase totals =	$1,032.56		$1,123.1760	$1,123.18	$1,123.15	$1,123.30