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	$176.69	3.860%	$183.5102	$183.51	$183.50	$183.50
Purchase #2	$178.59	8.480%	$193.7344	$193.73	$193.75	$193.70
Purchase #3	$124.94	12.454%	$140.5	$140.50	$140.50	$140.50
Purchase #4	$147.37	11.555%	$164.3986	$164.40	$164.40	$164.40
Purchase #5	$79.93	12.154%	$89.6447	$89.64	$89.65	$89.60
Purchase #6	$231.51	8.618%	$251.4615	$251.46	$251.45	$251.50
Purchase #7	$70.61	9.780%	$77.5157	$77.52	$77.50	$77.50
7 purchase totals =	$1,009.64		$1,100.7651	$1,100.76	$1,100.75	$1,100.70