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	$10.59	5.198%	$11.1405	$11.14	$11.15	$11.10
Purchase #2	$215.86	7.238%	$231.4839	$231.48	$231.50	$231.50
Purchase #3	$23.50	8.177%	$25.4216	$25.42	$25.40	$25.40
Purchase #4	$160.78	12.164%	$180.3373	$180.34	$180.35	$180.30
Purchase #5	$29.99	9.120%	$32.7251	$32.73	$32.75	$32.70
Purchase #6	$148.54	9.612%	$162.8177	$162.82	$162.80	$162.80
Purchase #7	$101.54	7.662%	$109.32	$109.32	$109.30	$109.30
7 purchase totals =	$690.80		$753.2461	$753.25	$753.25	$753.10