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	$72.89	10.390%	$80.4633	$80.46	$80.45	$80.50
Purchase #2	$202.98	4.633%	$212.3841	$212.38	$212.40	$212.40
Purchase #3	$195.85	13.762%	$222.8029	$222.80	$222.80	$222.80
Purchase #4	$250.88	6.814%	$267.975	$267.98	$268.00	$268.00
Purchase #5	$15.27	3.819%	$15.8532	$15.85	$15.85	$15.90
Purchase #6	$145.54	13.711%	$165.495	$165.50	$165.50	$165.50
Purchase #7	$72.33	4.461%	$75.5566	$75.56	$75.55	$75.60
7 purchase totals =	$955.74		$1,040.5301	$1,040.53	$1,040.55	$1,040.70