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	$118.95	4.177%	$123.9185	$123.92	$123.90	$123.90
Purchase #2	$175.97	3.843%	$182.7325	$182.73	$182.75	$182.70
Purchase #3	$119.46	7.858%	$128.8472	$128.85	$128.85	$128.80
Purchase #4	$235.32	12.427%	$264.5632	$264.56	$264.55	$264.60
Purchase #5	$228.34	9.277%	$249.5231	$249.52	$249.50	$249.50
Purchase #6	$52.25	6.499%	$55.6457	$55.65	$55.65	$55.60
Purchase #7	$156.25	5.316%	$164.5563	$164.56	$164.55	$164.60
7 purchase totals =	$1,086.54		$1,169.7865	$1,169.79	$1,169.75	$1,169.70