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	$73.71	11.437%	$82.1402	$82.14	$82.15	$82.10
Purchase #2	$233.79	9.705%	$256.4793	$256.48	$256.50	$256.50
Purchase #3	$176.87	10.513%	$195.4643	$195.46	$195.45	$195.50
Purchase #4	$55.90	8.671%	$60.7471	$60.75	$60.75	$60.70
Purchase #5	$241.94	9.301%	$264.4428	$264.44	$264.45	$264.40
Purchase #6	$162.37	12.136%	$182.0752	$182.08	$182.10	$182.10
Purchase #7	$50.34	11.627%	$56.193	$56.19	$56.20	$56.20
7 purchase totals =	$994.92		$1,097.5419	$1,097.54	$1,097.60	$1,097.50