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	$159.35	5.787%	$168.5716	$168.57	$168.55	$168.60
Purchase #2	$99.72	9.648%	$109.341	$109.34	$109.35	$109.30
Purchase #3	$89.93	3.116%	$92.7322	$92.73	$92.75	$92.70
Purchase #4	$179.40	3.632%	$185.9158	$185.92	$185.90	$185.90
Purchase #5	$152.38	10.167%	$167.8725	$167.87	$167.85	$167.90
Purchase #6	$186.90	6.555%	$199.1513	$199.15	$199.15	$199.20
Purchase #7	$225.65	9.828%	$247.8269	$247.83	$247.85	$247.80
7 purchase totals =	$1,093.33		$1,171.4113	$1,171.41	$1,171.40	$1,171.40