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	$39.29	5.709%	$41.5331	$41.53	$41.55	$41.50
Purchase #2	$237.42	9.557%	$260.1102	$260.11	$260.10	$260.10
Purchase #3	$167.26	9.310%	$182.8319	$182.83	$182.85	$182.80
Purchase #4	$165.38	5.550%	$174.5586	$174.56	$174.55	$174.60
Purchase #5	$133.49	6.704%	$142.4392	$142.44	$142.45	$142.40
Purchase #6	$123.55	3.178%	$127.4764	$127.48	$127.50	$127.50
Purchase #7	$13.63	5.792%	$14.4194	$14.42	$14.40	$14.40
7 purchase totals =	$880.02		$943.3688	$943.37	$943.40	$943.30